I'm surprised that custom bicycle frames with a fork can be made and sold as cheaply as they are especially considering what it costs to paint one. I've had a bit of experience is building frames from 4130 CroMo tubing. While these frames are more complex and have more material, they come unpainted. In fact, they aren't even primed when the customer gets them.
Curtiss Midget frame without steering or front axle: $5,500 Basic frame for a NASCAR car $10,000 Chassis for the average dragster $12,500 Chassis with suspension and steering for CART Car $75,000 Fuselage for Pitts biplane $12,000 Fuselage for custom Stearman Biplane $30,000 Engine Mount for 180 hp engine for Super Cub $3,000 (I can build an engine mount with less material and in less time than I could a bicycle frame.)
Jim