Depending on how fancy you get, they can run $25-$100+ for the razor itself.
The blades are double-sided and run about $7 for 10 on Amazon.com. Thus far, each blade has lasted a month with no problems.
Despite taking longer to shave, they have been the best shaves of my life, and I'm never switching back to regular disposable or cartridge shavers. Get a nice badger-hair brush and some good shaving cream or soap and you're all set.