Not necessarily expensive... just old... and only limited quantities exist. I know of only a handful of companies that still make ISA slots that are irreplaceable by anything that fits in a PCI, and those are definitely expensive.
For example:
http://www.mccdaq.com/isa-data-acqui...IO-DO192H.aspx
Closest replacement:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/202012
(Don't forget the special cables )
I forgot why the ISA bus offers the ability to have so many DIO lines... but I did know it at some point...
Ya... we use ISA's too... and not by choice...
--DDL