They’re free!  Broadband cards don’t cost anything.

What?  Isn’t that too good to be true?

Well, there is a catch.

Broadband cards are free.  But, to get one without paying for it, you’ll have to sign up for a data plan from one of the major wireless providers.  There’s also a small setup fee, often $25.    The data plan costs about $60 per month, and you usually have to sign a two year contract.  Also, some companies charge more if you download or upload more than a certain amount of data per month.

Another option is to buy a netbook or laptop computer with a built-in broadband card.  The card comes with the computer, but to activate it you’ll need to sign a contract with one of the service providers.  Many of the providers like Verizon, AT&T, etc. will provide a discount on the laptop if you sign the data plan contract.

So, all in all, a broadband card is free but it will cost you approximately $900 a year or $60 per month to use it to get high speed internet through a 3G  broadband provider.
For more information about what a broadband card is, check out this article.