How to value a used CD collection?

I have a pal that digitized all his CD's and is looking to sell them.  Approximately 500 high quality jazz CD's.   I expect he will be looking for a price for all of them.  I'd be keen to have them, but have no idea what that sort of collection is worth.  Maybe $5 a CD?, but he has lots and lots of stunning recordings that cost $30 or more.  Any insights would be appreciated.  Maybe I should just asked to match his best offer and see what happens.  

Any insight would be appreciated.  Thank you, Mark  
I recently sold all of my MFSL records (many still sealed) for $50 each. Considering that I bought each for $13.99, I was thrilled. I just saw one of them for sale here on Audiogon for $175. I mention this as I have a ton of CDs that I bought for an average of about $5 each. Half Price Books would give me $1 each if they recognized the name, and they didn’t already have several of the same title. My stash is mostly 60’s and 70’s rock CDs, not the uber sophisticated jazz CDs that your pal may have collected. I don’t have experience with Jazz recordings but I would try to lower his expectations. Unfortunately, used CDs don’t command the premiums they once did. Just my two cents.

Try checking discogs.
You only have to check to see just how cheaply cds can be bought for right now.

Reminds me a little of the huge vinyl dumping that went on early 80,s.

Hindsight is a wonderful thing.....
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elizabeth offers good advice. If the CDs are on an Audiophile label (DCC, MFSL and others) those discs will increase in value. Make your friend a best offer and see where it leads. I would be interested in learning more about his collection as well.
Happy Listening!
Ladies and gentlemen,
This potential purchase is a vexy one for the reasons you have mentioned.  I appreciate the feedback.  

Selling CD's on Amazon is a losing proposition with the nick they take out of the sale. I guess I need to investigate other less costly site to sell CD's if I acquire this collection.  

As an former market trader, what occurs to me is that will offer to match the best offer he gets for the lot of his collection.  I think that is the easiest way to value his collection... all at wholesale.  Cheers.  
is it an arms length transaction between market traders or a deal between friends ? I would offer what I felt was fair, add a bottle of Rye or Seasmoke and enjoy the good music and Kahrma....

Discogs provides statistical valuation ranges, however shipping on small orders can often exceed Cd value even w USPS media might figure that into the bottle of Rye

Sorry to throw a spanner in the works here, but if you rip your CDs, my understanding is you have to keep the cds as proof of ownership and your right to rip them in the first place. If you don't, you could be prosecuted, unlikely though that might be.

 Secondly, even if you back up the rip, you might want to re rip your collection to a higher quality storage medium , as I did.

 My concern is a more depressing one, what happens when I fall off my perch, I'm 70+ now. I have about 2500 LPs and the same number of CDs. I don't want to burden my kids with getting rid of them. Amongst that lot are some valuable albums, MFSL, Proprius, Opus, FIM and so on. Dealers I know, will rarely take whole collections and will give a derisory sum if they have too. So, any thoughts?

 The plan at the moment, is given some warning, to go through the whole collection, pulling out what I think is valuable and suggesting to the kids to E=bay them, or do it myself. For the rest, I would advise them to get dealers in and let them chose what they want, perhaps the rest can go to charity shops. takes less of a slice of the pie than either Amazon or eBay.

Reverb is cheaper still but not as well known as a site for consumers for buying used media ... Yet.

However one downside of secondspin is that just about ALL the cds on there are dirt cheap to start with.
David12 is correct, of course. What the friend is planning to do constitutes copyright infringement. Assuming, that is, that the material was copied to a computer hard drive as opposed to a medium for which royalties were included in the purchase price (e.g. Audio CD-Rs or some digital tapes).

-- Al 
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Of course but truly it is no different from what we all used to do back in the 70,s when we recorded our records onto cassettes.
Ostensibly to play in the car of course, nudge, nudge, wink, wink.
Never would have dreamt of keeping the cassette copy if I sold the actual hard vinyl copy...….
But on a lighter note that was really funny until I discovered upon death my parents had been renting the cute little princess rotary phone in the master.... for wait for it....30+ years...
A thousand for all assuming they’re in perfect condition. The most profitable way is to sell them in small lots on eBay. Or in some cases, if very collectible, rare or whatever, one at a time. 
Ironic that an audiophile mentions dial tone phones. Have any of you talked on one lately? In the hallway of my 90 year old home there is a black bakelite dial up phone from the 1940’s. We rarely use it but when you do the first thing you notice is that the sound quality is exceptional and that everything else you use for a phone sounds like crap. Even people on the other end will comment that it sounds better to them than any cell phone or cordless land line phones.

Agree with geoff. eBay is the way to go. Most sellers are getting $4-8 for typical pop/rock CDs of decent quality.

Some may think that is high but there isn’t another medium out there that presents that sort of value in music that you own.
I been been traveling for a while and haven't followed up on the transaction.  The best arrangement that I can see is if he sells 100 CD's off at a time, that I get a chance to match the dealers's offers.  They are all excellent CD's and I can peddle them off individually.