Amazing rumour! Microsoft already did this strategy all the all back in Xbox 360, where they took a massive loss to sell it at USD$/€299 (core system) and USD$/€399 (premium).
The point is, the Series X must match whatever pricepoint Sony has for their PS5 "Digital Edition". Sony has the mindshare with their games catalog, so Microsoft cannot command the price tag they should have.
Oh, and they also need to stress the Forza brand a little bit more. Sony trumpets GT everytime they can. Forza has not reason to be shy, in fact, it goes far beyond just the simulator thanks to Horizon (and the great DLC content that always follows in Horizon). Be shameless, show the hotwheels expansion of FH3, then the Lego expansion of FH4, and end the presentation with the tone of "something even crazier to follow, soon(TM)" -- because that's all that Sony does, hypes stuff that will take years to deliver.