I'm not naive or taking any of what they do or don't buy to heart or personal. I've sent in a large number of bags in the past few years and know that they pay little. I first sold to thredup a few years ago and payouts used to be a little better, and bags were all free. Most recently, they have started "consignment" where they list your items that don't meet the "upfront" requirements and pay you only if they sell with a slightly better (and USUALLY relatively fair price for no work).
Biggest problem is with consignment. If your item doesn't sell in the 75 or 90 days they give it, the item expires and they sell it for $9.99. YOU SEE NOTHING from that $9.99 consignment sale on your expired item. I have still never seen anything on the site stating that they can keep your consignment items after they've expired and sell them without paying you anything for it.
The upfront payouts are truly terrible now.
Bag 1 - 11 items from J. Crew, Banana Republic, Gap, Columbia, and a few other things. Payout - 14.05.
Subtract the $9.99 Bag charge so you don't have to wait 2 months for processing... $4.05!
Bag 2 - 16 items. Mainly J. Crew, Ann Taylor, plus BR, Gap, Old Navy, Michael Starts, and some others. $25.15 - $9.99 = 15.06
First bag 3 years ago - 13 items - Mainly Gap and old American Eagle Tee shirts - $25
Second bag three eyars ago - 26 items - Mainly old Abercrombie, American Eagle, Target, Old Navy, a little gap and express - $44.