Well he did make lots of money but you need to understand a regular computer programmer probably wouldn't have the experience to make these miners. Regular CPU programming is different from GPU programming. GPU programming I would say its a special niche and not too many people know how to do it properly. Basically GPUs have many cores unlike CPUs and you need to code it to perform the same repetative tasks as fast as possible and then compute the result.

So it takes special skill and experience to make these miners. Also AMD algos are different from Nvidia algos, so you need more expensive if you want a larger amount of miners. Hence he made tons of money because at the time, he was maybe the only coder which can make an ETH software. Only other people are maybe the ETH foundation, that wolf0 guy and Claymore. These guys are very old school.