I see your point, but that argument is always silly.To everyone that bitches and moans about bikes being too expensive, helmets, pads, bla bla bla
Go out there and make it all yourself, it's so easy and 'cheap' to do.
That said, I think it's easy to forget that we're in a niche industry. The potential market for full-on DH bikes is relatively large. R&D (including the cost of funding a factory team) isn't cheap, and that cost is passed on to the consumer.
You want to ride what the big boys want, you're going to have to pay for it.
I know guys who set up LLCs to house their part-time (amateur) rally expenses, and it's something I imagine any part-time DH'er could do, particularly if you have a few sponsors on board.