Don't expect any savings. my blackberry through cingular is $100/mo (900 minutes, unlimited data, 1500 text messages) and that is CHEAPER than the PDA plans.
And the phones are most definitely not free. After carrier subsidy my Blackberry was $200. That's one of the cheapest smartphones they offer. The other ones were $300+ after subsidy.
Don't expect any discounts, this is a high dollar luxury item and the bills are going to reflect that. Cingular doesn't really make any money off the phone sales, that's apple's profit area, so the monthly bills are gonna be HIGH.