Just depends on what your time is worth. If you have spare time, tools, and don't mind buying some materials, why not?
Years back I was buying my first set of traps, and thought I'd save a buck and get the plain wood Heritage Lakers. "I'll just varnish them myself!" I sez, "Won't take but a minute!"
Good lord, by the time I got them all taken apart, sanded, poly-d, sanded again, coated again, and reassembled in a semi-reasonable time period to avoid losing ALL the tiny parts.... I might as well have built them from scratch.
Next year, just bought the finished ones. I'm lazy like that.
But believe me, like Lion said, I see portions of traps that I like a lot, and think about picking and choosing and building one nice trap. GasBlaster and Gunner have done some of that, and made awful nice traps. More trouble than I want to deal with, tho. Again... lazy. I certainly admire ambition in other people. God knows I don't have much of it myself.