Microsoft Store offers preorder downloads of Gears of War 4 for Xbox One and Windows, bundled with a $10 Microsoft Store Gift Card for $59.99. Assuming you'll use the gift card, that's the lowest price we could find by $10. (We saw physical copies of this game bundled with a $25 gift card for the same price last week, although physical copies do not include the Play Anywhere download code for the PC version.)
Microsoft Store also offers preorder downloads of Gears of War 4 Ultimate Edition for Xbox One and Windows bundled with a $10 Microsoft Store Gift Card for $99.99. Factoring the gift card, that's the lowest price we could find for a download by $10. (Again, we saw physical copies of the console version for the same price with a $25 gift card last week, although it did not include the PC download code.) This edition includes the season pass, four day early access to the game, Steelbook packaging, and access to the Xbox 360 Gears of War Collection (featuring the first four releases in the series.) The game is expected for release on October 11.