Define expensive. 200$? That's the cost of the plumber's time, and now I've got that tool forever. That and I've gained knowledge and know how to fix or build something that I didn't before which is something I take pride in.

In my experience, there's been very few things where it makes more sense long term to just pay someone else to do it so long as you're willing to do a little bit of learning.

I wouldn't say always. I usually ask my friends if they have the tool and borrow it, or buy it knowing someone will likely borrow it in the future.

Tool libraries are a pretty neat solution to this. Some local book libraries are getting into it as a way to expand services.

Fortunately most of the tools you don't use once. The few you do tend to be the types of tools a pro would rent as well.