$100, plus the cost of the mandatory microSD or SSD you'll need to add to even install the game on Deck, plus the $50 discount for the Series S if you have a modicum of patience. The difference is more like $175-200, and last year the Series S was $100 off for Black Friday. Assuming the game is targeting holiday 2023 for Xbox, you could potentially grab the Series S + BG3 for under $300.