One of Amazon’s Deals of the Day today provides a Microsoft 365 Family 12-month subscription with a $50 Amazon Gift Card for just $99.99, a savings of $50. In other words, the $50 Amazon gift card is free.
That makes it kind of a no-brainer, and because you can stack these things, you should be able to add this year to an existing subscription.
You can find the deal here (affiliate link).
This deal is good for today only, and possibly in the U.S. only (sorry). It expires in about 16 hours as I write this.
Thanks to Neowin for the tip.