I quite liked that first router in Wilfy's link. It shows what is possible with wood, however I suspect the guy always planned on redoing it, and alot of the components were picked for ease of building rather than cost, as it wasn't really a cheap build component wise.

If you want to cut costs, and you've got the time/motivation to redo things, use wood for large flat sections, but design it so you can then replace with aluminium as time/money allows. And spend the money saved on making sure the other parts are good quality and upto the job. From what you've said, you're not aiming for high accuracy, and you are realistic about what you aim to achieve, so go for it.