Plum District ThreadUp

Has anyone heard of this? It seems like a really cool concept but I'm not so sure. I would love some feed back!
Plum District is offering a pro membership to Threadup.com for $20.00.
You post your used kids clothing on line and someone picks it, and you mail it to them.
You find clothing that someone else posts and pay 5.00 for the whole box +shipping.
Think of it as a big garage sale by mail

Ok here is where I am thinking this is a good deal. With the Plum district deal you get a Pro membership.
What's that?
Well Threadup teams up with NEW clothing stores. One new one each month. You can pick from a box of NEW never been used clothing and get that for $5.00 a box! + shipping.
Now that sounds like a good deal to me. A whole box of new clothing shipped to my door!

New to Plum District?

Plum district is an collective buying site offering deals at a discounted rate. They have one national deal, that is good for anyone to get in on and is redeemable online. They also offer deals that are just your city. Head on over to Plum District  to sign up. Buy the deal you are interested in and an email will be sent with a voucher number. When you are purchasing your item, enter your voucher number at check out and redeem your Plum deal!