I think you're being a bit low on the estimates there for eBay though....
Classic Amiga stuff can get nice prices still, even for slower stuff. A Trumpcard SCSI card just sold for >$100 I believe, for instance, because it had 8MB RAM on it. Admittedly that's rarer than a 2091 but it's still a slow Zorro-II only SCSI card.
Point is, you could get much more than those quotes at auction - but you quite possibly won't. That's Amiga dealing for you!
Not just Amiga stuff, either. Those 1571 you mentioned that were said to be $15-$20 tested? Well, one just sold on eBay.co.uk untested except the light came on, and sold for £50 (that's what $80?). A C128 that was for spares+repairs sold for $20.
If you sell the cards seperately, particularly, be sure to sell them worldwide on eBay. That stuff is worth a lot more over here in the UK, for instance.