I spent $200 on materials for my last build, a 2 string bass with one pickup, split into 2 actually, there was a savings! but I already have a workshop since I'm a carpenter. I have hundreds of dollars worth of gear in my shop, and over a decade of woodworking experience. if you have a buddy with a workshop, buy some band aids and get going!
its profoundly satisfying to play an instrument you designed and built yourself.
come to think of it, I think $200 is what I originally spent on materials for the first bass I built back in 84, a fretless, originally a 4 string, now it's a five. and with upgrades it's material costs come to about $350 probably. however, time is money too, if I paid myself to build my last bass, I'd want about 2 grand for it based on hours put in at my carpentry rate. its a labour of love though.