I have a HTC Desire S. I don't remember the upfront cost, but it wouldn't have been more than $50 and may have been nothing. I'm paying $59/mo for 24 months. For that I get:

1.5Gb of data
$500 of outgoing calls (90c/min - yeah, our call costs are ridiculously complex, but we don't pay for incoming)
Unlimited text
And the phone is unlocked.

Mind you, 1.5Gb/mo phone data is huge for me. I got used to managing my data back when it was 256Mb/mo and never lost the habits.

Wade.