It would cost around 4ish bil. I have a manually raised manually geared(didn't bot or use botting money for the gear) barb that can do mp 10 fairly easily, the gear is worth nearly a bil.(before botting i had to manually flip items in the ah to slowly build up gold to get the gears i wanted.) Since the bot doesn't perform like a human would, you'd need even better gear to compensate for the lack of human efficiency. So yea.. around 4 bil or more.