There are very few machines that a collector doesnt move on after a while... its what happens. Some titles are CORE titles that never get moved on but these are only a few compared to the titles that go through your hands.

A mate looks after you with the pricing on some pins, that fair enough, but if several years down the track you move them on for more than you pay im not sure what it has to do  with the mate anymore. If there is some moral obligation to split profits with the original owner each time you make a few bucks on a pinny sale then i guess i dont have many morals.
And yes.. selling pins is a business as it covers the costs of the next purchase. I recently sold 3 games to fund one game.. each sold at a slightly higher price than bought for... i dont owe anyone anything and seller of new game obviously did alright or he wouldnt have sold it either.

Buy your mate a few beers etc, but if you buy at $1000 and manage ti sell at $3000 a few years later.. then bloody good on you.

I once bought a house from a mate... several years down the track it sold for less than i paid for it.. did my mate stump up some money for me?? Like hell he did.. is he still a mate?? Of course!