The first official keyboard and mouse for the Xbox is $250 and only works with 16 games

Apart from the price and game availability, there's a whole debate whether a keyboard and mouse for consoles is a good idea.
TweakTown

You can now play Xbox-only console games on PC

TL;DR: Microsoft now allows Xbox Insiders and Game Pass Ultimate PC subscribers to stream select console-only games via Xbox Cloud Gaming, expanding access to over 250 titles without installation.