...wouldn't that be $12 billion that Apple has to poach MS engineers with, then?

Sure. Which tells you which company M$ considers the more central threat.

Yep, but with the msft focus on the cloud, their priority is to take from goog.

Additionally, people buying OSX computers isn’t really a bad scenario for Microsoft. MS office is quite popular on OSX and iOS and people spend more on that than they do on operating systems.

If Apple really invested in OSX it could be a threat to windows, unfortunately, combined with the high cost of the hardware, OSX's downslide means it's stuck to its current pro market...

Apple is making investments in OSX: Catalyst, T2 chip /security, Touch bar support, iPad mirroring, airplay, arm64 support (speculating), SwiftUI. Metal/GPUs. Core apps: logic pro, xcode, playgrounds and brining more iOS apps (news, stocks, apple tv app, apple arcade with subscriptions). I also suspect with arm64 will come better cameras (lidar perhaps), beefier GPUs and neural cores. all of this running on macOS.

What kind of investment do you think they need to make to be a threat with Windows? If you think they should be trying to "match" windows with things it does, it would be a bad strategy that isn't winnable. Throwing away money. At least with their current approach they are levaring strengths (verttical integration, mobile dominance, etc) to build something that could leapfrog windows one day. Especially if the user journeys that span into other products (hw accessories, phones, etc)