First of all, there is an option on the website to check a brand and see what they pay so there's no surprises when you get your offer... DO YOUR RESEARCH PEOPLE. I paid $98 for a Judith March dress, I look on ThredUp and see a JM dress for $38, I look at the consignment price if I sell a JM dress to ThredUp and it's $1.40. So I didn't bother to send anything to them.
However I've purchased over $2,000 worth of clothes from ThredUp for about 25% of the price. I purchased a $178 Pea in the Pod shirt for $28. That is a STEAL people. So I will GLADLY buy from there but I will NEVER EVER sell.
Side note, shipping is SLOWWWWW. I don't bother paying to upgrade but sometimes it takes over a week. Expect to pay return shipping. I've never dealt with a person from TU so I can't attest to customer service.