If you have the tools and space to work, DIY and putting the money towards the best possible drivers is a great idea. I built my speakers.
Absolutely. I go DIY constantly because it's not only a good value but enjoyable. Currently completed projects:
SB Acoustics Bromo
Mark Audio Alpair MS11 Full Range in Nostromo Cabinet
Econowave in Realistic Nova 8b
This project - The Manzanitas
There are probably more that I've forgotten about but I agree, bang for the buck is all there and so is the fun of building and woodworking. Only issue is that if you want to sell your DIY project to fund another you take a bath where as with a used product you can usually sell it for what you have into it so to me it's usually the proposition of used vs DIY.
For my open baffle project it's a done deal and has been selected. There are so many zero cost open source DIY projects out there that I can do myself that I personally don't see much need in spending thousands on products that have only a few hundred dollars in driver parts. I can do the finishing work/assembly myself and that is where a lot of the bulk of the cost lies.