How much does a mb of data cost when not on a contract with data on it?

I have a really old contract ish and i got my bill back today and it says its £15 extra for internet usage, so i hop on the iphone and it says i've used 58mb of mobile data (the rest i've used with Wi-Fi) but this seems extremely expensive? Is it right? My contract is with vodafone if that helps

What does your contract say? Usually contracts start at 200mb to 2G. Do you have a data plan? Contact vodafone.

You should check their website to see all this info. It changes from carrier to carrier.