I wish I could select multiple options.
I find satisfaction in building it myself, and I enjoy wheeling a rig I built myself.
I enjoy (usually) the act of creating something.
I end up with it exactly the way I wanted it.
It's cheaper than paying someone to do it.
Since I built it, I know exactly how to fix it. I also know what's likely to need fixing.
It's true that you can usually buy a built rig cheaper than you can build one. If you have a specific way you want everything built, the only way to do it is build it yourself, or pay someone to build it. It's either going to be a lot of work, a lot of money, or both.
X2. I do fab work as part of my job. I find it very satisfying when someone looks at what I've built and is amazed with the quality and finished product. And when I see vehicles/machinery I've built and the users are happy with it, it's just that much more of a confidence builder. It is very rewarding work.