I haven't had this problem with any of my R1s, so I would suggest that before he goes and spend $700 on valves, that he does a little research. How hard is it to call a couple of shops?
I don't see lots of R6 owners posting that they need vavles on the R6 forum, so it's not too common.
It could be a legit problem, or not. If it is, it's expensive, and yes, another motor should be cheaper - but you also don't know that the new motor won't have the same issues.