I dont think an engineer in China is cheaper than in Europe. Thats not my experience.. At least in the big cities, they cost more or less the same as in Europe.
A Friend of mine owns a business and hired a guy in China full time. Works out to be ~40k usd/yr. His work is really good. If you’re going via a business to get outsourced work you’re just getting ripped off imo.
Sure, I can get a student to throw together a React frontend here also for very little money. If I want highly specialized knowledge about camera drivers, network protocols or low level programming, the story is different.