I have an iPhone, with 150 minutes per month phone time, 150 free text messages, unlimited mobile Internet. That costs € 30 per month (about US$ 37). If I use more minutes or more text messages, I pay per extra minute or message. I don't talk a lot and send text messages a lot, so this is more than enough for me. You can also get more expensive plans for the iPhone with more minutes and messages.
I guess most plans work that way here (the Netherlands) - usually you get a certain number of minutes / messages for a flat rate, and anything you use more costs extra per minute or message.
There are also prepaid phone
cards here - you buy a prepaid card for for example € 15 or € 30 and then you can call or text until you've used the credit.
Incoming calls are always free, but there are some annoying text messaging advertisement things that try to get you signed up to their "service", you pay for text messages that you receive from them, and they try to make it hard to find out how to sign off from the service. Companies that do that have been warned by the telecom authorities recently.
There are usually no bandwidth use limits on Internet connections (whether mobile or on a fixed line) here in the Netherlands. In other European countries that's different, for example many people in Belgium complain about the bandwidth limits that seem to be common practice over there.