Hello Bahram,
Try taking a look at these links, they may be helpful to you:
https://www.cgtrader.com/blog/infographic-best-selling-3d-models-and-practices
https://www.cgtrader.com/forum/topics/how-to-attract-customers-to-your-3d-model-and-increase-sales
https://www.cgtrader.com/blog/instructographics-boost-your-sales-with-simple-techniques
https://www.cgtrader.com/blog/how-to-make-your-3d-models-more-visible-key-tips-to-improve-your-sales-2016-12
Cheers,
Eddie, CGTrader