More expensive = better?

IMO it will depend on what the higher price is for. Are you paying a higher price for one amp over another because there are higher quality components used? Are you paying a higher price for a proprietary design or circuit board? Are you paying a higher price for a better built product that brings tech support and help.

Or are you paying a higher price for an amp that is not built well with low cost components, off the shelf circuit boards. Are you paying more to cover marketing and advertising costs that add nothing to the sound. Are you paying more for an amp from a company that has to pay retail rent, heat, electric, and employees to sell them. Are you paying more for an amp that is sold by an independent dealer with a 200% mark up yo cover his business cost.

I would end with the answer to your question as being yes a more expensive amp can sound way better based on price if you are putting your money into areas that add to the sound not the fring costs that add nothing to the sound only to the cost.

"Incredible that people think they listen to an amplifier.... For sure they sound different but most of what we listen to relate to the room acoustic coupling with the speakers...

Money dont buy audio experience with upgrading gear...

Acoustic do....

I dont say that acoustic is important i say it is essential...."

Of course you listen to an amp! You also listen to the preamp/dac/tt/cart/cables. You are assuming that nobody sets up their audio rooms properly. When you start talking about hifi, you should have the basics already covered, and you start with the room. If your room isn't treated properly, why would you think of wasting your money on hifi equipment? 

Probably because buying gear is easy. Room treatment in a science. Gotta find the right folks to do it. How do you find that right person? In a big city it might be easier. Who knows when a room is "right"? Some yahoo might come in and screw it all up. It's pretty easy to slap up some panels and stuff. My cousin has treated his room with fake Christmas trees! He must have 15 or 20 in there. Seems to work pretty good. Just weird. Any ideas?

"Incredible that people think they listen to an amplifier.... For sure they sound different but most of what we listen to relate to the room acoustic coupling with the speakers...

Money dont buy audio experience with upgrading gear...

Acoustic do....

I dont say that acoustic is important i say it is essential...."

Sorry to hear you were not able to hear differences in amplifier sound.  I upgraded mine a few days ago.  Put it in the same position, etc, etc, with only 1 other upgrade, which was a new speaker cable.  It sounds vastly different, I could the vast improvement of it.  The price of the old and new amp, the gap is from $1K to $5k, so perhaps its easier in my case.  Perhaps it's harder to hear those differences between $10k vs $20K amps.

Not all the time, of course, but it's not a bad rule of thumb to start with, at least with certain types of gear....