I don't sell on Gumroad, but I do sell on Etsy, and use a somewhat similar software (albeit much more robust) called eRank to help spot trends and get ahead of the curve. You should look into amending this product with some more robust features:
* Utilize the API to let a Gumroad seller import their actual Sales numbers, to help further refine your reviews to sales numbers.
* Connect with google to spot search trends that lead to Gumroad products
* Run some sort of AI analysis to help the seller understand their copy is failing them for SEO, etc.
Check out eRank, and look at their offerings, and you can get a lot of ideas on how to grow this product from $50 once to $10+/mo.