I recently started a new game and went all out mage. When I got to about a 65 or 70 MA the normal armourers, gadget/inventors and gunsmiths wouldn't let me in their shops! Told me I was too powerful, I thought I was going to be stuck with a whole heap of bits that I couldn't sell. After putting some points into haggle and gaining Expert level, I've found that most anyone will now buy anything. One other thing I found after a particularly productive trip was that even if the shops ran out of money they still took your stuff. I didn't realise what was happening until I had handed most of it over... luckily I had a recently saved game.