Lifetime pricing

I really like xmind. I use it for studying. I have maps about pretty much everything related to the veterinary area. I've been using it for more than two years now. 
I would like to support the devs, but where I live, the monthly princing in dollar is equivalent to 1/4 of my monthly supermarket bill - meaning it would have a impact in my finances. So... Is it possible to make a lifetime princing? Make it pricier, but forever. I believe it would make more likelly that people in same situation as me buy your product instead of just using the basic features forever and never repaying you.