I can buy new in that class (Hobart) for around $450, Eastwood for $300 so knock off at least $100 - $350 or so. I would not give more than that, personally, because I can buy new for little more or factory refub for about the same. They all come with the regulator, so that adds zero - you'd take off another $50 if it wasn't in there.
>I'm sure you con't have a bottle which will cost a min of 100 bucks for a small one.
You ain't priced bottles lately. Try $300+
140s can't do AL as far as I know - not enough power or wire speed. 175 and up 240V units can do that and many come with the spool gun.