It's not that rare, those frames you welded were someone else's product. And that poor inventor likely earned more money for less time then you did to boot (granted he would have more invested on the front end, but still...).How true, how true. - Everybody who thinks they are going to "invent" something and make a million dollars is kidding themselves.
Try to start a business from the ground up on a product you "invented" and you will have a whole new meaning of going broke. - You got a better chance of hitting the lottery.
Making your own products as a machinist is almost cheating, since you naturally can design for manufacture.
The world needs job shops and product shops. Some people are better at one than the other, get in where you fit in.