I doubt the Iron Slug sold for 495k. Also, a 5* weapon is worth more than twice as much as a 4* version of the same thing, for the sheer amount of CE it would take to unbind and create. Callahan is definitely the more popular choice between the two lines as well. That said, IAS medium is decent and would fetch 1-1.5k CE if it were 3* and maybe 2.5-3k CE if you were patient at 4*. Good Luck in your sales, just wanted to give you some insight as to why there are not that many biters.

Edit: NVM. GG at necroing a 2 month old topic johojuki, the seller and item are probably long gone by now.