I am all for feeding developers.
DevComponents develop DotNetBar - a whole bunch of tools for use in building applications using VS - excellent tool VERY competitively priced.
Their competitors are in the $1000's price range, but DNB is in the $100's.
It's a yearly subscription that costs $264 for single licence when you first buy (299 with source code), and then somewhere around $100 off to renew your subscription. The great thing with their pricing model is that even if you don't renew for many years you still get the discount when you decide to renew.
Like Scirra, they are constantly releasing updates and bug fixes (usually every Friday), they have a very active forum, and they always fix bugs as soon as possible.
Scirra could use a similar model and I would be more than happy to support it. Maybe have a similar system that they have now, free version, and personal and business licence priced accordingly.
But always stay competitively price - GM and the like are definitely over priced.
Just think of Adobe - do you like them, only want a relatively few well funded customers, or would you rather have the whole creative community using your tools.