This is the reason I made a complete inventory of parts (no matter how small) for my old PC's - just before I hit "buy" on an auction site, I double check.
Just recently I bought 11 ISA cards for about $10 from a Polish site, pretty much for one card in there that is worth around that amount (to me anyhow) with a couple more interesting ones. There's a couple modems, those are going right in the junk pile. The rest of the cards (a lot of 8 bit I/O and 16 bit IDE/FDC controllers, as well as full 16 bit I/O cards) are selling for $5-$15 on eBay, so yeah, up they'll go once I test them out.
About the MS disks - I went through my floppy inventory recently (actually it's an ongoing thing, prepping for GOTEK archiving) and I did find quite a few bad-sector damaged MS disks (Windows 3.1 and DOS mostly) which I think I will use as coasters. I can't bring myself to throw them out!
Youtube channel- The Kombinator
What's for sale? my eBay!