I despise RAMBUS as much as anyone else.... but I'll sacrifice for performance.
If a DDR P4 set up cost equivalently to an I850 P4 setup I would be buying the I850 + RDRAM.
Better performance for equivalent cash outlay.
Brand loyalty is foolish. I am not going to sacrifice my money to get something that is inferior to another solution. And right now I850 is the superior option.
I have companies I like, I have companies I favor. I have companies I dislike.
But I will not knowingly purchase an inferior solution just because I dislike the company, I do not have enough money to throw around doing that. I want the best I can get for my money.
I buy whatever offers the pbest price/performance ratio.
And in the question it specifies a hypothetical situation in which an RDRAM + I850 + P4 cost no more then DDR + P4X266 + P4, in such a situation I would buy Rambus because they offer the better price/performance.