When announcing the iPhone 4, Verizon said that they would be adding the ability to use the iPhone as a mobile hotspot for up to five devices.
MacWorld has discovered that the feature will cost users an extra $20 a month. That's on top of your current plan. That's not entirely surprising, given that it's the same price on Verizon's other phones. It's also worth noting that you are given 2GB a month, any gigabyte past that will cost you an extra 20 bucks. We are assuming that going over that automatically rounds your total up.