Personally I think it's a lot of effort for devs to support anything below ICS now, it does eliminate some potential users though. I think the normal way of doing apps is either a free stripped down version and a fully featured paid, or both versions fully featured and then ads on the free and then no ads on paid.
Just to add I'm not sure if this thread goes here, mods might want to move it where you'll get more answers and help. Hope I've helped a bit.
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