What's the point on buying from small business/indie dev. if they might become big and greed eventually?
Allow me to reformulate to a broader level:
what's the point of living if one is going to die no matter what?
The point is to try to do something.
The worst criminal is still a human being. Does that mean we should all commit suicide, now, the 8+ billion of us, to never risk becoming the same criminal? Hopefully not.
By supporting a (small) company whose work you appreciate you give them a chance to keep on doing good work, maybe. Things can change... and when this happens you can change with which company you chose to spend money.
I had been a customer of Apple since the early 80s. I quit some 6-8 years ago because I realized how not the same company they had turned into.
Edit: typo on the date I started being Apple's customer.