I am going through this problem right now.

I told customers the price and it would not move and all updates will be free, however I am about to release the second version of the product.

It is significantly more stable, faster, more features, better designed, and one of the best applications I've ever made.

I want to recoup the time spent on it, not to mention my sales from v1 have started to drop and I want to bump that up again. Maybe I'll release it as version 2 for pay but initially at a discount? I do not know. Suggestions?