KC2IXE is right. I said you could get into APRS for around $100, but to do it, you've got to be willing to hunt for parts and do some of your own assembly. Around here we've seen retired business radios for about $30. Add a TinyTrak or OpenTracker for between $20 and $30, and a OEM GPS board for about $25, and you are set.

http://www.byonics.com/ (TinyTrak)
http://n1vg.net/opentracker/ (Opentracker)

On the other hand, if you have a laptop, you can put together a radio to sound card interface cable and skip the TNC all together.