Wrong page bro, I think you want to use the classified (To do that right click the item in your BP and click - sell item) ;)- You posted a price suggestion instead :P

For your trading needs

http://backpack.tf/classifieds

http://www.tf2outpost.com

this is in regards to changing the prices of ALL strange grenade launchers, in tf2 keys. if you want to sell a tf2 item for dota keys, there's a nifty site called tf2 outpost.