Never happened to me. But then if I am approached by these types of "offers", I just disregard. I'll bet if I want to go camp at any one of their parks, I can just drive up there, register and pay the daily rate, and they will let me pull right in and stay. And probably not nearly the money you're talking about. And if not, then I'll bet there is another C/G right down the road that will.
As a matter of fact, we do stay at a condo type park in Alabama. They sell lots for $100K. The nicest park we have stayed at. First time we stayed there a guy came by and asked if we would be interested to hear their 'pitch'. I said, "No...this is a very nice park but, I am not interested in buying a lot." His response was...OK...Fine...But we have to ask. Hope you don't mind? Have a great stay with us."