1) Here in the UK I'd expect about £15 to £20 each, less through discount/online retailers. The 3.5 PHB is currently £11.29 on Amazon UK, but my nearest FLGS is asking £16.99
2) Yes. I'll at least buy the PHB, and assuming I like it I'll buy other 4e books.
3) Yes. I've spent loads on 3.5 but...