I like to buy big lots (small lots are fine too, but, they often aren't worth the price+shipping)
Here's my general guidelines on buying and/or consigning USED stuff to sell:
1) I do a quick estimate of value based on KEH, eBay and other known Used sources
2) I tell you what I think the "street" value is
3) I offer you:
Roughly 1/3 (up to 1/2 if I know it'll sell fast) the street value to buy outright (after factoring in costs and unsold/discounted remains this leaves me a 20-30% margin which is typical and fair in the retail environment)
To take the item(s) on consignment for a 30-40% (depending on how much work I think it will be to sell) fee. We agree to the minimum you are willing to let an item go and I try to get as much over that as possible.
4) If your lot is a total mash of mixed little items, I'll usually just make a low, but reasonable, offer on the entire lot. I don't like bookkeeping, so, I avoid doing consignment on items valued under $100.
DO NOT THROW ANYTHING AWAY!!!
I have seen too many customers, all very happy people, come to my shop with their Beseler 23C and nothing else. Cool. It's worth a little something. Not so cool is when they're missing the lenses, carriers, timers, and all the little stuff that Really adds up. Sadly too many people think it's the big thing (the enlarger, the N80, the old strobe) that's worth something and they toss the truly valuable gems (the untouched Spotone Kit, the Moose Filter, the softbox). They leave happy, but not with nearly as much cash as they could have had.
If you own a store, are a distributor or manufacturer, please see my new thread "Suppliers and Retailers" coming up soon.
I hope I haven't given away too many of my "secrets" and that this encourages you to consider me in the future as a source of liquidating your unused items (or those of your well-meaning friends who try to give you, the 8x10 user, a cute little Vivitar enlarger to use) so you can free up space and buy that next box of film.