Here are the prices for complete GPS systems.  The first column assumes you have a laptop available to help decode and display the packets.  The second column is for a complete handheld solution.

Manufacturer Laptop Based Handheld
BigRedBee GPS Approx $389* Approx $489**  $785***
GPSFLight Approx $600 > $1000
ATHA Aerospace $739 (Canadian) N/A
Loki $750 N/A

*using a DJ-S45 receiver   ** using a DJ-S45 and a Byonics TT4     *** using a Yaseu VX-8R

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