The analytics might not be entirely without value, but I'm guessing people are paying the submission fee because they want you to build their product and give them an entirely reasonable 12% of the proceeds rather than for feedback (which they could solicit on web forums targeted to their intended niche without paying a dime). As far as I can see they don't learn much about the actual commercial viability of the product, simply that some unqualified people love or hate it.

Have you tested the price point? Assuming your business model is ultimately based on selling viable products rather than submission fees, removing the entry fee or lowering it to a nominal amount might actually benefit you in terms of better submissions, particularly since you already have the community to filter for crap.