This site is not for hardcore deal shoppers. There are many options for buying cheaper than threadup. Even if you get a free box from a promotion, you are still (according to the fine print) supposed to eventually list your own box plus pay the $11 shipping. So for a small box (even if stuffed full that's not a lot of clothes), you are paying $11 plus however much money your clothes were worth that you had to give away (plus $5 if you didn't get a "free" box). For $11, I could get a couple bags worth of clothes going elsewhere.
This website is awesome! Parents can trade a box of clothing that their child has outgrown for one that is their size. It's free, you just pay shipping! The only problem with it is there doesn't seem to be a lot of poeple with older kids sizes (pre-teen/teen) sighned up such as 14/16 or 18/20. It would be great if we could get more poeple involved. If you deciede to join and would like a month of extra benefits put in referral (or friend) code:49724.