(Session timed out. Should have been posted under license discussion - Sorry.)
Hi Mike. Good idea to discuss this openly.
I bought several of your extensions (sandbox, invite, ajax connections, adsense) totalling about $120 at the time which, to me, was a 'big' spend for two personal and multiple speculative, so far non-profit making, sites.
On the features side, I bought them because they were unique, interesting and useful etc etc.
... but before your head swells

...
On the finance side, I justified the purchase on the basis of :
- flexibility on which extensions I used (or didn't use) on which of my sites
- ongoing free upgrades (I'm not sure of the exact wording, so don't bite head off!)
- ability to use the extensions on multiple sites making the per site cost reasonable
All the sites are mine, under my control, being developed as time allows.
I would be 'a bit unhappy', if I was asked, now, to pay higher license fees for multisite use.
While not a developer of components, I currently spend at least two days a week testing/debugging and feeding back test results and suggested improvements into Joomla! and other 'community' projects and helping where I can support other's through forum posts.
... so as mentioned earlier, there are different ways of 'contributing'.
I can understand your need to get a workable model and hope this thread helps you achieve it.
Great work. Cheers.