Available shields and shield ideas

I've been taking a look at GSM/GPSR modules for a shield. I have came across 2 different ones already developed for the arduino, one for like 70euros and the other for 99euros. That seems expensive to me. Would it be that hard to take apart an AT&T prepaid phone that you can get at Best Buy for $30 US and etch your own board.

I'm just fishing for thoughts on this.