Is there a cost increase for a data plan with an iPhone?

I have a Droid X2 with a data plan allowing for 2Gb of data a month from Verizon. I'm considering buying an iPhone 4 from a friend but would like to know if the cost for the same data plan on the same carrier would increase just because its an iPhone

Smartphone data plans costs is the same for androids, iphones, blackberries, windows, and palms

No, there would be no increase in your case. You are already paying the Smartphone Data Premium and yo I would basically just be getting a different smartphone. The only exception to this would be if you. Are getting a Blackberry, a number of carriers charge extra for "Premium Blackberry Web" Services.