Where is the significant point of diminishing returns on hi-end turntable?

Oilmanjojo has this in good perspective, imo. The question I would pose to you is: Do you hear the difference and is it meaningful to you? Then, does making that step from the $10k rig to the $25k rig still allow you to have a superb phono stage? Amp? Speakers? Cables? Or would you have build a BETTER sounding system overall by stepping back a bit on the investment in just this one part of your system?

Over the years that I've invested in this hobby, I've always found the investment to be a stair step process. I HEAR more of what's going on in the rest of my system as I upgrade in an area and then assess what will make the next biggest improvement. But I have always planned on DOUBLING the investment in each step up that staircase. Small incremental steps just keep shunting money down a tube that never stops draining cash but without providing material improvements in sound.

All this said, as Oilmanjojo suggests, "with 10-25K, you should be able to put together a reference vinyl system that will please for a long time. But there will always be something better."

But if you're making that next big investment, and if you are seriously committed to vinyl, then the best place to make that investment is in the turntable/arm/cartridge front end. What doesn't get extracted from the vinyl to begin with is never heard in the rest of your system.

I'll close with one final observation: The magic is in the details. Scrupulous attention to setup, to fine tuning, makes all the difference between superb playback and indifferent sound. You can often get far better sound than you ever expected if you really understand what is needed to finely tune the setup of a vinyl front end and take the time to do it. 

Dealer is recommending aestetix Rhea signature.  Not an IO but are you very satisfied with the phono stage?

This is that never ending cycle, mmporshe. :-)  The Rhea Signature is very good. The Io Signature is in the next league, and the Eclipse moves a further step up from there. With all three, use a medium output (~0.4mv) cartridge and you're in a great place.

Yes, I've had the Io Signature (with dual power supplies and volume control) for 15 years and I'd not change it for anything else I've heard except the Eclipse version. And, like everything in this crazy hobby, the dual power supplies make a difference.

mmporsche: Yes,i hear a difference between the $10 and $25 setup. Not 2.5x but that is diminishing returns at its finest.  Definitely better, just wondering where to stop. Almost sounds like there is no end game.

No, there is no end game. As oilmanjojo said, there is always something better. For me it was the Walker Audio Proscenium Turntable and Aesthetix Io Signature phono stage. Now the next step would be the Io Eclipse upgrade, full Walker Audio Diamond V update, and Air Tight PC-1 Supreme cartridge. Will I do that? Probably not. But would it be better? Oh, yes.

:-)  But now you're going to have to take the insane plunge into: 

1. Seriously cleaning your vinyl to get the best sound you can out of the grooves ( My DIY Approach to the Ultrasonic Cleaning of LPs). 
   
2. Find the best pressings (Steve Hoffman Music Forum) and purchasing multiple copies to compare.
3. Adding a magnetic optimizer to your record playing ritual.
4. Getting the cleanest power to your equipment without adding noise and distortion artifacts.

The fun doesn't stop with purchasing the turntable. Now you have to work on the details to get the best sound from it.

mmporsche, you could just jump right into the deep end of the pool along with me. Slipknot1 is selling his Walker Audio turntable because he's downsizing due to a recent illness. He's asking just $25k for the turntable, integrated linear tracking arm and Magic Diamond cartridge. I'd be happy to put you in touch with him. Unfortunately, he's on the opposite side of the country from you near Philadelphia, but he'll split the cost of shipping.

whart, excellent discussion of the journey! What you describe very closely matches my experience, also.

Goodness people, pay attention. The OP has 5,000 LPs available to him, he grew up in audio, he's lived with a very nice system including analog. He posed a simple philosophical question in his original post and the commentary that has ensued has ranged from constructive on-point discussion of his original musings to telling him how to build an audio system to calling him an idiot and a child. Please READ the OP's comments and do both him and the rest of us the courtesy of trying to stay on topic.

Sorry. Rant over.

Orpheus: When the OP went from his original question to 25K, that changed everything, because that’s way past "diminishing returns"

This is a fine point, orpheus. You presented your perspective on the question he raised. For you, $25k is already past the point of diminishing returns. Okay, that’s one experience and value proposition. It wouldn’t be mine; it’s clearly not the OP’s.

More importantly, though, is the BASIS on which we each evaluate and determine the point of diminishing return.

There clearly is no absolute monetary figure. As in so much of the investment we each make in our audio systems, we are dealing with: 1) what differences do we hear, 2) do we consider the differences material GIVEN OUR LISTENING PRIORITIES (which are different for each of us), 3) how much enjoyment do we anticipate from that difference we’ve identified, 4) what discretionary budget do we have available, and 5) to what alternate use would we put that discretionary budget and how do we value that alternate use?

To simply state a monetary figure just means that FOR US this is the figure at or beyond which we’ve answered items 1-5. In the OP’s situation, he answered these items with a pretty clear determination that he was okay with this discretionary budget figure at 25k - all 5 questions were answered to his satisfaction.

The implicit question was "Will I find a similar compelling rational to move to an even higher expenditure if I had the opportunity to hear something even better than I’ve heard thus far?" Seems to me that this answer is different for different people; there are only factors to be weighed not proscriptions.

Whitestix, I regret to have to tell you but AJ Conti passed away recently. See:
https://www.facebook.com/permalink.php?story_fbid=1188155424599920&id=179180802164059

Basis will continue but we have lost a terrific audio designer. I agree that he developed some excellent turntables and tonearms.

Here is a good example of "Don't feed the trolls," folks. Two posters (or is it one?) with 4 posts and 3 posts to their names. The tone is abusive, the comments completely off-topic. I've reported the abuse. I hope others will do similarly so we can move back on topic or move on in general to discussions of more interest. Seems like we've worn this one out and @mmporsche may be wishing he never started the discussion.

...so I’m just asking what do you consider "suitable"?

Orpheus10, my apologies for the delay. A bit over a dozen years ago, I was on a similar search to the one the OP finds himself. Over our time in this hobby, my wife and I have made it our practice to choose for what makes a difference in our musical enjoyment and to change equipment only infrequently. When we have made an equipment change, we’ve sought to make it a material improvement in our enjoyment of music and not make lateral moves. Typically, I do the research, come up with candidates and then my wife (who is my listening partner) joins me in the listening evaluations.

A dozen years ago, our search was for a "final" turntable that would be the turntable to which we could expect to end our audio ventures still listening.

The turntable we settled on is one we probably could not afford today, but the price at that time, while still very much a stretch, was one we could manage. We’ve never regretted the investment for an instant.

That turntable is the Walker Audio Proscenium Gold turntable. You can find the review I posted on Audiogon here:
https://forum.audiogon.com/discussions/review-walker-audio-proscenium-gold-signature-turntable

I'm sure I've seen that one in "Stereophile". 

No, not on Stereophile but it has certainly been in The Absolute Sound (Jonathan Valin) and Positive Feedback (David Robinson).