Excel is probably the most useful application ever made. Pretty much every professional services implementation and technical account management engagement is done via excel.

For me, I've used it for budgets, to-do lists, etl, reporting, financials. Its data handling utility is pretty much unmatched. It's super easy at this point to see anything with it.

It's well worth any price for sure. It's really the only reason I have a 365 subscription at this point. And like everyone else, I doubt I've used more than 2% of it.