I think I kind of know what he means. My full time job is a military vehicle mechanic for the National Guard, I sell parts and build trucks for people, but the money I make pays to maintain my own collection. Sort of a self funding hobby I guess. Not sure how you would catagorize it.
IMO, you categorized it perfectly. You have to fund a hobby like this, and when you buy parts at GL, you get more than you need, so...
There is no way I could afford my first vehicle without SS support, and if I was to ever go to brick and mortar, or a commercial vendor of trucks and parts, I would be happy to pay for advertising at that point.
I think it is all a great idea, as long as the SS site can make a fee off of them. Otherwise, they lose their revenue steam from the vendors above. You have to treat all commercial vendors the same, IMO.