All:
Here's a cost comparison of map update prices from the manufacturer's web sites.:
Garmin Nuvi 2008 North America Map Update For most Nuvi's: $60
Tom Tom Map of North America Update 7.25: $100
Magellan 2008/2009 North America Map Update: $80
Pioneer's seemingly(?) overpriced AVIC Update: $120
As you can see, Pioneer's North America map update DVD costs twice as much as Garmin's, 50% more than Magellan's, and 25% more than Tom Tom's.
edit:
The Alpine one for the Blackbird is about $70. Rumor has it that the Eclipse updates are MORE expensive than all of these, but I've been unable to verify that for sure...