In my experience and humble opinion, high poly models can and do sell for many reasons. However, you should provide them with high-quality textures, and plenty of quality renders that are created from the same native file format you are offering the customer.
3d printable models also do sell, but you have to offer them in a variety of formats and you have to have items that are unique in some respect. Offering 3d printable models that just point cloud Photogrammetry Software captures of everyday objects with horrible topological density and very low-resolution textures as STL files will not sell very much. There are millions of those things out there for free already. However, if you can create printable models that can also be used in other aspects of a 3d pipeline but also have the option to be 3d printed, you should do quite well.