I'll pick boofhead up on that; it is definately not more expensive! Yes you pay for the launch, and while you're training the emphasis is on shorter flights (all the hard bits are at the start and the end, let's face it), it's still cheaper. Once you get used to staying up there, it's a lot more cost effective. (I fly/flew both, more powered now). One thing it is expensive in is time however (compared to powered). It's not a turn-the-key exercise, and you need particular conditions to stay up (not all VMC days are necessarily any good for gliding).
It is a somewhat different game, though you'll have a huge headstart, you'll use your feet more, look outside more, and mapread more, rather than doing stuff by the numbers. You'll also get there quicker if you don't turn up with a 'I fly powered, I know it all already' attitude - not suggesting you have that attitude, but I've witnessed the groans at launchpoint when such a pilot arrives/departs
