[Q] Just got offered 600 keys in max bets for my Howl .08 MW ST (it has stickers). I didn't take it... MISTAKE??

I really need an expert to help me put a price on my M4...

I've been having problems for months now on how to price this item

SS: http://steamcommunity.com/sharedfiles/filedetails/?id=603602705

http://steamcommunity.com/sharedfiles/filedetails/?id=603602385

Thanks all!

Please any opinion would help!