if I recall correctly I bought a T8 rockjacker from auction for like a year ago for around 18k. It depends on what tier you have on yours but it should be worth something similar to the regular rockjacker. Value of weapons has only gone south since that tho so I'm not sure how much it down to now. I'm in the market for a new gun but I'm holding my horses until mayhem rewards are announced if not a super super deal pops up before that ^^