Change membership prices

I don’t think you can do that, and if I am not mistaken, it would be a Paypal issue not a s2M issue. After all, your customers registered with an understanding that the price will be X. If you change that, you are “breaking that understanding”.

I would suggest you have their membership terminate at a certain point in time and offer them a renewal (re-subscription) with a new price. That is what a magazine subscription would do in a way, letting you know in advance so you can opt out if you don’t want to pay the higher fee. Of course, they tend to just TELL you instead of ASKING you, but that would be close enough.