Errrrm to be honest I think $100 is a bit low for a minimum investment at this stage of the ICO, they are offering a 60% bonus, this should only be available to larger investors.
I think they will reduce the minimum investment when the ICO gets to a later stage and a lower bonus %.
Exactly, the large bonuses are only when you invest at least 10 ETH most of the times, with pre-sales this is less and during main sale the minimum gets pretty low
It's almost guranteed that the inestment minimum will drop for the actual ICO, we're talking presale and its completely normal for the minimum to be higher, and yes it requires a larger investment to reep the benefit of the big bonuses at this stage of investing. Their trying to i think balance the early investment bonuses with the presales availability to keep things fair now and longterm.