YAGNI. There's nothing wrong with not acquiring new skill either. It depends on how soon/often you will need to use the skill in the future. Also on how urgent you need to do it if the need arises.
The trick is having enough skill to be able to evaluate the professional you're going to hire. I've been bitten by this before both in my personal and professional life. If you don't know enough about the field even someone with only a marginal amount of knowledge about the topic can seem like an expert.
As programmers we see this all the time when non-technical people make very bad hiring decisions. It's a chicken and egg type problem for a non-technical (co-)founder to build a good team because(or find a technical co-founder) he/she needs a good programmer to evaluate potential hires but they can't make that evaluation themselves.
I would expect myself to encounter exactly the same problems others encounter when trying to hire good programmers when I'm trying to hire some other kind of expert in a field I have little experience in.
It also depends on the amount of revenue you can generate if you hire a professional and get on with your work.
If we assume that the professional's fee is constant (doesn't depend on your income), then someone with very high income can waste only minutes on the task before it would have been cheaper to hire a professional, whereas someone with low income can devote a few hours to learning how to do it themselves and still make up for lost earnings by avoiding the cost of hiring a professional.
You an other comments seem to only balance cost and time lost, but doing your own curtains, for many people, is also fun, rewarding, interesting, and a very good way to change focus from professional or personal issues.
I find most of the benefit of learning new skills is in how they supplement other skills. I may very well never need to drill into masonry or have dry lined walls - by knowing that they exist, I can ask better questions.
