$150 is a lot of money on top of the cost of tickets, hotels, and travel to get to the Disney parks. I know the parks get crowded and the lines get pretty long. I can't say that I would or would not go for the additional charge. It depends on how much money I've spent on other things and if people accompanying me are paying for it. The money spent on FastPass would definitely cannibalize other experiences. I would be less likely to dine somewhere nice or pay extra for other attractions.
Regardless of whether or not I paid for it, I think this move would do harm to Disney's image. If I paid for this or if I saw people who had paid for it getting ahead of me in line I would grumble a lot. I'm not a fan of FastPass in the first place to be honest. It extends the wait for people waiting in the normal lines. Disney could make a lot of money off charging for FastPass, but would it be worth upsetting average customers and potentially cannibalizing revenue from other sources?