Precious Faces is a (merchant) resource for everybody who wants a few more options to create versatile and unique looking characters.
You are able to use them to refine some of your own created morphs or to create completely new faces with it. Yes, you can sell your ceated faces, there is no limitation.
Some morphs are a bit on the extreme side but that will give you a wider range to create. facial features. Some fundamental knowledge how to use morphs on G8Fs lashes or how to remove morph vertices is needed if you want to create commercial products.