Blowpipe is intimidating but sometimes it just fails...if you can get poison comboes going and you're streaking 20+ then it really gets op but other times it may not hit at all:/
Value of the account would depend on stats, quests completed, unique items like firecapes etc, and wealth(if any). I've never sold an account so i wouldn't know too much about the 2 day ban pricing though:P
I remember about a year ago i was banned on all of my accounts for goldfarming macro or something just because i would transfer money from my botting accounts to my main. Idk if they still give these bans but i would be cautious