I'm not saying I didn't gain a lot from it, I really really enjoyed it and want to do many more.
Also, I could cut the wood and do everything pretty quick, because my shop is already outfitted with wood (I had to order the birch ply though because I use other stuff), saws, sealant, routers, etc. To build the actual box only took me an evening because I've been doing stuff like this for years. But, by the time you add in finding the driver, designing, reading, bullshitting, going back and forth, buying toys, etc. etc. the benefit is the process and enjoyment more than saving the money on the subwoofer. Also, depending on how much money you make, it can start to be difficult to justify the time if you don't look at it as a hobby, if you do, then its well justified.. That's all I'm saying.