Yes, I get it. So if you get a dirty and maybe broken a7750 for 30 usd, why not provide a clean one for 60 usd? Make that a total of 330 usd then.
You said it would increase the price dramatically and I say it would not. The point is, as you have mentioned already, that probably 95% of the rep buyers don't care. They could easily provide better quality checks and cleaner assemblies even without having to increase the price, but then then everyone would profit a couple of dollars less..
You are buying a 300 usd rep and then have to pay another 200 usd or more on a 30 usd movement for a service unless you can do it yourself. What's the point? You are proving that in theory the A7750 is capable of being a good movement. In reality it is not, imo.
I didn't say you can get an ETA 7750 watch for 300 usd. I said that 300 usd in China is equivalent to probably 900 usd or more in a western country. And for 900 usd you can get a watch with a clean ETA 7750. Why can't I get a clean A7750 watch for 300 usd in China then?