The 2 speed bottom brackets are expensive because they are not mass produced like Shimano's IGH hubs and perhaps Shimano will offer a 2 speed bb at some point to expand he range of their IGH hubs... I have heard rumours of this happening.

The range on the Alfine is pretty decent and is best suited for commuting and touring where you have more bottom end for climbing and might max out at about 80 gear inches at the top... unless you are racing this is a perfect top gear for most people.

I get by pretty well with a 3 speed IGH... my better half loves her 8 speed.