If you bill for both directions, then you are in the MINORITY of hosts.
Period.
Most hosts bill based on the HIGHER of the two directions (in webhosting case, almost always without exception outbound).
Of course you could do 1Mbit/sec in both directions on a capped line, but you don't get "more" that way really, as what use does a webhosting customer have for inbound bits?
If anyone out there wants cheap inbound, let me know. I'll sell it for pennies on the dollar compared to outbound.
-Phil