In my experience it has been, Being their to help them with their questions and/or struggles to help them grow with you. Also, That you are a product of the product makes a big impression on them too. Not only being a member but using it in your business as well.
When you are a product of the product and you can answer any questions because you have consumed the product as well they have more respect for you and you can even position yourself as an authority in their eyes too.
When your Liked And Trusted They Continue To Buy and Follow You!
Communication, Communication, Communication with your prospects and specially your buyers.
Hope this helps,