As for the paid product, we issue a no-questions-asked refund to anyone who requests it within some reasonable amount of time (30 days usually). Even with this, our refund rate is less than 1%.
E.g.: "Pay only after you earn your first 100$" but along with "NO WARRANTY" and "no support" and maybe "without IDE, only cmd line tools and SDK" but that would be an extreme - still, better than nothing.
I think this will _tremendously_ boost your user base.
All in all, you will cover a new target market with retaining the existing market.
Anyway, thanks for the great product!
EDIT: the market you actually will loose (in "no support" users) - are the users who didn't succeed. Not sure if you can track the numbers, that would help to determine if this business model will be positive for you.
That said, I totally understand if that's not a market Xamarin wants to be in.