I use Apple for 19 years now (Classic II

). Last june I bought a new 21.5" iMac in a APR store. Right after connection I noticed the famous yellow tinge. Because of work activities I could only bring it back after a few weeks. The screen had to be replaced. That took 3 weeks.
I got the message from the store: "replaced screen, tested and ok"
But when I checked it at home, a yellow tinge was visible right away. At a different part this time. I need the computer for my study and my work so I asked for another iMac. 'Not possible'. My money back then? 'Not possible'. It had to be repaired again. That took 2 weeks.
"Replaced screen, tested and ok" and... Right! Yellow tinge again. The 3rd screen.
Now I realy wanted my money back. But that was impossible. "Apple has the rule blahblahblah..." After threatening to ask help of a consumers organisation they came with the proposal to trade the iMac for another one with the same specs.
We checked the new iMac in the store and it had a yellow tinge. Also the last one they had in supply showed yellow tinge. The only iMac that didn't have the tinge was the demonstration model on the shelf of the store. And still they refused to give me a refund. But they soon did after I gained some legal advice.
Ok, so today I got my money back and travel to another APR in this area. I go for the 27" this time. I check the screen in the shop, from a distance. It looks ok, slightly yellow lines across the borders, but I've seen worse so I take it. At home, when I'm installing the software I notice a tiny black line... and a dot... and another dot. First I thought of bad pixels but with a magnifying glass it appears to be fragments of black plastic.
What is the matter with these screens? The box says "Assembled in China". Is iMac 2010 just a piece of deteriorated chinese junk?