Basically, there is a bit of a captive audience scenario going on. The carriers (AT&T, Verizon, Vodaphone, etc.) with lots of subscribers and good networks are looking for ways to milk more money. While there is probably no valid technical reason for the cost, those big carriers see it as an easy revenue stream. Most business people can get a $9.99/month fee absorbed by their company or at least right it off on their taxes as a business expense, so the companies push these services to make more money.

Some, like Verizon, actually cripple GPS competitors on their networks to funnel customers to their service. But, carriers with less customers or weaker networks need to compete on price, and are unlikely to artificially jack up the price on non-essential things like GPS service.

But, those big carriers see it as a way to extract more money from those with the ability to pay and a desire/need to remain on that network. Perhaps I'm cynical, but that's how I see it.

Oh yeah, there are alternatives, such as Infospace's FindIt! program, Google Maps, and of course BlackBerry Maps. While they may not have all the bells and whistles, they can help fill that niche for free.