A lot of Xbox One games (minus some exclusives) are on the PS4 as well. The PS5 is almost fully backwards compatible with PS4 games (physical and digital) that can be found super cheap, and it also plays newer PS5 games too.

So 400 bucks or not, you'll get way more mileage and value from the PS5 with access to 2 console libraries. Only, check if the price is legit. The PS5 is 550 new, and it's tough to find, so if this is true, it's a steal. If you prefer Xbox, the Series S and X will still give you more value than an Xbox One (again all the games from there are playable on the Series, plus some OG Xbox and 360 games).