Have you built speakers before?
I've done a lot of DIY, especially with wood, and including speakers and crossovers, and I'll tell you right now that it will always take more time than you think and be more expensive than you think. Especially if you need to buy the tools to do it, such as saws, saw guides, router, router bits, drill, drill bits, hole saws, sanders, soldering iron, veneer tools and clamps. Clamps alone could run a couple hundred dollars. You'll also need supplies, like sandpaper, stain, brushes, solvent, veneer, polyurethane, glue, etc. A good stain like General Finishes will run $35-50. And you'll need batting, internal wire, terminal cups, grill cloth, feet, and crossover parts (which can be hundreds of dollars), etc. Even wood is very expensive right now.
It will also be more time-consuming. If you're inexperienced you will make mistakes. And if you are experienced you may tend to want to push your skills to the point of making mistakes. Mistakes cost money.
Unless you're highly skilled, I would say stay away from DIY unless you achieve personal satisfaction from the idea of creating things. If it's just about saving money, you likely won't.