I wanted to get one of those cards that lets you get mobile internet from anywhere. How much do they cost?

Many times the cards themselves are free with a contract, however a contract and mothly charge is required similiar to phone, and there is a monthly charge associated with it. You could expect a cost of at least $50 per month. Depending on your cell phone, you may be able to add tethering to your package for around $20 that will allow your laptop to connect thru your phone via the blue tooth connection.