I would love to see some pics of the one made with lumber!
I bought my first one from John @ US car tool when he was first starting out. If I recall it was around 1k to $1200...something like that. A few years after my buddy bought one from him and he had upgraded the head with bearings. Basically its a trailer hub like you can buy from tractor supply. This makes a huge difference when spinning it.
At the end of the day the most important thing is to take your time leveling up the car and centering on the rotiserie. It can make a night and day difference. Right now I have my Cuda (E body) on it and I can spin it over 360° by myself. At no point does it get out of balance. This is the fifth car I have had on a rotiserie and I get better at mounting them each time. I nailed it this time. The tip is if it doesnt rotate easily keep adjusting it until it does.

I priced some 2x2 box tube a month ago and it came out to $14 a foot and you had to buy 20 feet! Granted this was at a local place that is usually a little high but damn! I told them they could keep it.