What's stopping you from doing this since it's incredibly lucrative?
Plumbing and building have static value. They will always do the same thing. The value of code is highly dependent on the context. SWEs are highly paid because they can create systems which can be reused and built upon over time.
Hiring an engineer to build a system doesn't make sense when it handles $0 in GMV, but makes a lot of sense when it handles millions in GMV. Tech companies are asymmetric bets.