Of course it is, and this entire website is half devoted to "is X worth paying more instead of the cheaper Y?" type of threads. You also have to have your head in the sand if you think forums are not places where people put forth opinions but only rock-solid supportable fact. It's certainly valid for a given poster to express an opinion, especially if the OP asks the question or opens the discussion, as to whether spending lots of money on a bike, part or whatnot, is a waste of money that might be otherwise better-well spent.