Hawaii is VERY expensive to get to. Any discount airline flying there seems to have folded in the past 18 months and flights are pricey. Then you have the usual island issue of everything being way more expensive as everything has to be flown in.
Route 66 is a pretty old road and not much happening on it at all. Check out some forums etc on american road trips, thats what I did last year and did Pacific Coast Highway instead and it was brilliant. Although some people like to do parts of route 66.