I downloaded one of your free models to check it out.
Pluses:
• Model itself looks very nice.
• Subdivisible
Minuses:
• Textures are just flat/diffuse textures, no normal, spec, roughness maps etc
• No names on textures, so it takes forever to import the FBX into Blender and place the textures.
> Nothing worse than a nice looking model that´s either impossible to work with or wastes your time.
• Studio/environment included: Could be a plus, but I´m not sure why it would be needed.
• Imports with everything upside down (possibly an export issue)
SUGGESTIONS
• Fix textures
• Fix import issue
• Consider making Blender version
• Increase prices about 100% in general when above is fixed.
Hope this is of use :)