Exclamation marks in little yellow circular stickers on CDs... what do they represent? I am guessing it's a warning of sorts, perhaps in place of parental advisory?

Reduced prices. That's all.

I thought it was meant they were remastered versions of older albums. I've seen them side to side with the original releases on New Order albums and they cost the same. hmmm.

They are official MIDPRICE albums.
Oldies. Not deemed good enough to make lots of money anymore.

I have seen those on older imports but I could be wrong. Sometimes, they are cheaper. I assume that they must use them worldwide.