Since they just focus on Azure and just milk Windows with ads and let it rot nowadays, I'm guessing it must be very profitable, otherwise they would stop.
I'm sure Azure is profitable for Microsoft. Microsoft are not even trying to sell development tools (the category of tools that would include LINQPad) to Linux devs.
They don't care about development tools period anymore, they just make most of their business on the cloud and most of it being very dependent on Linux.
