Because it's a market rule if you wanna withdraw your skin into Real Cash like on OPSKINS(most safest website) you can't get full price ..Biggest sellers like Bogla selling skins for 75% market price .If you wanna sell for full 100% price your skins for Real Money or 07GP ->$$$ you never sell it cuz no1 have profit on it.
Sorry I'm not english hope you understand,and if you have to sell any skin what request above feel free message here or add me on skype "rmfan95"