Quality can not be subjective. The same product can perform the opera house orchestra and school band and you clearly hear the difference. You can write a beautiful melody and beautiful harmonies, but to make a bad arrangement, and poor mastering, and this is bad quality. A good quality you need to spend a lot of time and therein lies the problem. To stay on the mind and keep the sales trend is sometimes necessary to sacrifice quality. I hope that my message was clear.
I think when talking about quality, price point comes into play. In this regard the entire audiojungle catalog is stellar, and in many cases masterpieces.