Potentially sketchy scam paint apps on the Mac App Store. Dominated by high-praising reviews, some all occurring on the same date. I bought one (the first) and that application, though in top paid section was low quality with the same marketing materials and screenshots and price range under $10 as some of the others in this list. Apple actually gave me a refund for that, so that was nice.
I would totally only buy a paint app if it had hundreds of good reviews at this point and very few negative reviews and came from a company that had other good apps in the store. A limited free version to trial would help.