At $29, the USB-C version of the Apple Watch Magnetic Charger is priced the same as the USB-A version that's long been available.
The USB-C version of the Apple Watch Charger is only available in 0.3m, and is not available in the longer 1m and 2m lengths. It's not clear why Apple has decided to only offer it in the smaller size, but additional chargers with longer USB-C cables could be added in the future.
Apple has been selling Lightning to USB-C cables designed for the iPhone for quite some time, but there was no equivalent option for the Apple Watch, so it couldn't be charged via a USB-C power adapter or a USB-C Mac sans adapter.
The new USB-C Apple Watch Charger will ship out in one business day and will be available in Apple retail stores starting next week.