-2 camber should not cause any significant tire wear. I’ve been at -1.5 F/R for almost a year now. In this specific case, I’m not sure how bad the dynamic camber is on a S4…and I didn’t know that changing the camber on the s4 was so expensive, but in general, for anyone who drives “spiritedly” or gets out to the tire-shredding auto-x courses a few times a summer, the extra camber will most likely save them some outside tire wear.