A developer that starts to raise their prices because of great success might actually do this because his costs are also raised. For example, he might have started alone, but because of the big customer base he build up over time, he had to hire people so support tickets can be solved/answered in time. He might have started at home, but because he had to hire employees, he had to rent some space in an office building.
It's not always just greed. Sometimes there is a good explanation why prices get higher.
I'm only saying this is a possible explanation for higher prices, I'm not saying that it's the only reason. It's more than plausible that in some cases, it was indeed all about greed.
I want more... more... MORE!!!!
