″...and that’s why you can’t haggle with store clerks.”
That is the norm, at least in the US. But a friend of mine worked at Macy’s, and she said customers would occasionally try to negotiate prices. They were often successful.
A quick search online found that it’s possible to haggle at a lot more places than I had realized: 11 Retailers Where You Can Negotiate a Lower Price (wisebread.com).
I consider this somewhat ethically dubious, though. If the clerks are paid hourly, they don’t have their own “skin in the game,” so there’s no way to have a fair negotiation.