B1-3 were sabotaged very early into production, so the cost was less
than the inconvenience. B4 was where they dumped all the money, and it
was very iffy if there'd be a 5, until the Minbari came up to the plate
and offered to help finance it. For Earth, which was almost wiped out in
the war, it's more a matter of self-preservation.

jms