It's not pricey when you compare it to the subscription price of a lot of stand-alone devices.
It is well worth it for me, but I live in one of the worst traffic areas in the country: Southern California, where the same drive can take between 20 minutes and 2 hours. Having live traffic means that not only will it give me a different route depending on the time of day, it will keep checking the information along the route and possibly reroute me.
One time I was going from Long Beach to Santa Monica, and it had us go on surface streets the entire way, kept rerouting us, and it took about 35 minutes. When I looked at Google maps, the most direct route (via freeway) was so clogged, it had an trip length of over 2.5 hours.
Don't tell Navigon, but I'd pay $25/year for their live traffic feature.