Yes, they just use data so if you've got an unlimited plan (highly recommended for a BB) and aren't roaming internationally they're free. If you use a lot of them you may want to consider IM+ or BeeJive, both are one time fee applications but they could save you valuable app memory.
It's a different rate for BIS vs. BES customers I think, but my BIS (consumer) Verizon plan is a line item on the bill "Mobile Broadband Connect 5GB" for $30/month.