At their current rate of making EBITA, Microsoft will make back the $69 billion that goes to ABK within 10-12 months. The real question is how long IF ever ABK generates $69 billion in revenue or another lifetime IN THE RED venture for Microsoft. Like XBox, Danger, Kin, etc...
I suspect this is far too simple of a take. At a baseline, ABK is profitable. A super quick Google shows ~$2.4B of revenue in Q2 2023 at a 26% operating margin. But sure, ~$500M in profit a quarter would take a long time to pay back a $70B purchase price. But there's also how they can leverage ABK's past, present, and future catalog to enhance game pass and the whole of PC/XBox gaming.
As a Game Pass subscriber, it makes me far more willing to keep subscribing if I know there's now this entire huge library of games, some portion of which will inevitably come to Game Pass. That makes me want to keep using my Series X (or to buy what comes after the Series X, much as I bought the Series X as an upgrade to my XBOne without hesitation), or eventually get around to building a gaming PC and buying games for that platform too.
All this as a hardcore Apple user with a house full of Macs, iPads, and iPhones. Devices that, I will add, I never game on, nor would I
ever spend a dollar on gaming any of them, as my full-throated rejection of Apple's legendarily pathetic and condescending attitude toward gaming. So through gaming alone, Microsoft has brought me into and made me a money-spending customer of their various ecosystems, when otherwise there would be no reason for me to have even a Microsoft account. I have zero exposure to anything else MIcrosoft-related in my day-to-day business and technology usage.