Before the Electrohub was the Anycopter.
It was a 5", plywood, disk sandwich, using 1/2" square dowels for booms. I bought spare boomstick at Ace Hardware. I built and rebuilt mine and eventually gave it to a school. Many hobby shops and craft shops sell 1/4" plywood. If you can handle soldering a wiring harness using 14awg wire, it's probably the cheapest quad you can build.
When you buy plywood make sure it is free of knots and gaps. When you buy boomstick make sure it isn't warped and buy spares. When you drill holes, make them straight through booms and evenly spaced on plywood.
One of the beauties of such a system is your ability to control the length of the booms. Longer make for more stable copters and can accommodate longer props (within reason). Shorter makes for a quicker, more twitchy copter for shorter props and higher KV motors. If you go long props and low KV motors be sure your booms and how you mount the booms can take the torque.