you're also getting some rather sophisticated hardware with a kyma system, whereas reaktor is (obviously) just software.
not that i'm calling it cheap regardless....
kyma
"A basic Kyma System includes a CD-ROM containing the Kyma X software (for both Windows and Macintosh platforms) with over 1000 presets and 350 prototypes, the Kyma X Revealed! book, a Kyma FireWire interface with 3 meter FireWire cable and 0.5 meter Capybara cable, a Capybara•320 sound computation engine with four processors and 96 megabytes of sample RAM, four channel 24-bit A/D and D/A converters (up to 100 KHz sample rate), dual two channel 24-bit AES/EBU digital audio interface (up to 100 KHz sample rate), word clock input, VITC and LTC time code inputs and outputs, and MIDI In/Out/Thru. Available with desktop or rack-mount side-panels."