It's always tempting to build it ourselves but it often means we're now building the library instead of the thing we wanted to build on top of the library.
I'm currently building an office. By that I mean I've done all the work to coordinate building an office. I also ran the network wiring and will do the drywall. I built a few of the framing panels and contracted out the rest. I LOVE building things with my hands but it's been a year and my office isn't done. I have a kid and a job and pets and a million incomplete tasks. Sometimes I do it because I was poor and think about money and other times I just want to know I can. When things finally need to get done though, the cost benefit analysis is usually done pretty quickly. Nobody is paying me to do framing and the time I get to spend with my family is finite, so I pay.
While my interest in computers resulted in IT career, I don't have the same expectations for all the DIY things that I do. I understand those are just hobbies that make life more interesting.
And I think that I still understand when to buy instead of DIY. :)
The thing that I think is important is to have the confidence and ability to know that you could DIY even if you aren't choosing to in a given situation.