Though counters vary quite a bit in pitch, when it comes to large numbers there seem to be rules which force them to be Heiban:
However, what about intervals of 100? NHK will often show the pitch just for １００. For example, here's １００本(ひゃっぽん{HHLLL}):
So what would the pitch of ２００本, ３００本, ..., ９００本 be?
