Natal will cost around £100 when it launches this October, Edge is reporting.
The site's unnamed source - who previously broke Gears of War 3's announcement and release date - said that the motion sensing tech will retail for $149 in the US (£103, based on current exchange rates).
It will also be available with an Xbox 360 Arcade console for $299 (£207).
If correct, Natal will be more expensive than Sony's upcoming rival, Move, which will be bundled with a game for less than $100 upon launch later this year.
The site was also told that Microsoft's planning to release Natal on October 26, although this date could move by a few weeks either way.
"Microsoft expects to sell millions and millions of Natal units in its first year on the market so you can expect the software launch line-up to target non-traditional gamers," the source said.
"A major marketing campaign will also play a key role in attracting and educating the expanded audience about Xbox 360's controller-free revolution."
It definitely won't be called Natal either, as that's apparently just a working name.
Microsoft said it wouldn't comment on "rumour or speculation".