Well, I have an idea. Why not sell it for a normal game fee, and then charge 10-20 bucks for each upgrade? HTC would still be getting paid quite often. And it would still be good if you had a $10 a month payment on top of that. Right now you're getting out about 2 new versions a month, that's $20-$40 right there, plus $10 a month normally. While I don't expect updates to be as often as they have after release, I think it is a plan that works for both parties involved.
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"Do unto others....and get your head blown off." -Brethon