For people who are able to purchase credit ahead of needing it, Newegg has $100 Xbox e-giftcards (which I know from experience can be used towards basically anything Microsoft sells including Surface devices, movies and TV, games, Xbox devices, etc.) on sale for a 13.12% discount. You can buy up to five $100 e-giftcards for a total cost of $434.40 using the code below which may automatically apply itself.
I personally love buying credit like this on sale and then waiting for discounts on games I want because it means I’m able to get an even bigger discount.
This may not be for everyone, as you need to be able to afford to buy it upfront before you need it, but if you are in that position, this is a great deal.
BFDBY2A365
https://www.newegg.com/microsoft/p/N82E16832416743?Item=N82E16832416743&