Pixies reunion is not any different than most reunions nowadays... it's just that they're honest about it. I mean, do you really think Pavement reuniting, releasing a best-of and going on a tour (isn't it called Goodbye Tour?) playing all their hits is any better? Even Atari Teenage Riot reunited, while they've been saying for seven years they wouldn't in respect for Carl Crack...
Not to say ALL of them made it for money purpose only (in the case of ATR especially, seeing their political views and how their new shows aren't expensive at all), of course, but Pixies clearly aren't the only ones. Dinosaur Jr also said they reunited for money, and they also hated each other.
Also, not to say the Pixies reunion was good (though some liked it. to each their own, i guess)