I've been told that Promptus sells a reasonably (under $10K per PRI) priced
switch that will accept up to 11 BRI's from the phone company, and give
them the appearance of a single PRI for the PM-3.
BTW, Ameritech's (Illinois) PRI pricing isn't too bad.
I just got a quote of $600/month (plus $2800 installation) for a PRI
(data and voice) including the T1 circuit. While the initial cost is much
higher than for POTS, the recurring cost is "only" 25% more per-channel.