For us I think it would depend on the amount of salary we are making. Right now we are both still young and early in our careers so we don't make a ton of money. We have AP's, and being about to pay monthly was a huge selling point for us. Right now we pay about $25/month, which in the overall monthly budget is next to nothing. So even if the price of an AP doubled, paying $50/month still wouldn't break the bank. Now, if they get rid of the monthly plan or prices extend past double, I think we would have to reconsider. So, I guess that puts our breaking point at around $1000 for an AP.
It seems most people are more concerned with resort prices and I agree. I know staying on property is amazing and we love doing it, but we don't have kids and don't spend much time at the resorts except to sleep. We have stayed at many Holiday Inns that have nicer rooms than Pop or the All-Stars. Obviously they lack the theming and overall Disney feel, which can be important. However, if we know we are going for a more relaxing trip, versus the run-around-like-crazy-people, 14 hours in the parks trips, we will stay at a moderate and there we really see the value in staying on property. With the rooms being nicer and the theming more 'adult' we can justify it more. I didn't have much of a point in all of that, just thinking out loud