I've been able to add some SPs to my 2002 Heritage football set via Beckett, and also have gotten some good deals on autographed cards. You're right, a lot of the listings are at (or even above) book ... but there are some decent deals around depending on what you're looking for.
I buy off Beckett Marketplace frequently and even though the prices are high, there's a lot of decent stuff to be bought. Just a couple of days ago I received an order of some nice Blakes [paid around $80 for them] and even though I overpaid, it's worth it because of the cards.
Basically it depends on what you need and if any other place has it [eBay, etc.] because the Marketplace is expensive.
I think the biggest reason for the high prices is the lack of any cost to list them. Plus, if you are listing on Beckett marketplace, you have a tendency to believe Beckett prices which are way out of line anyway
Comments
2005 Origins Old Judge Brown #/20 and Black 1/1s, 2000 Ultimate Victory Gold #/25
2004 UD Legends Bake McBride autos & parallels, and 1974 Topps #601 PSA 9
Rare Grady Sizemore parallels, printing plates, autographs
Nothing on ebay
James
Basically it depends on what you need and if any other place has it [eBay, etc.] because the Marketplace is expensive.
Collecting Jeff Blake