So then, haggling should be illegal and banned or is this idea of "one price for everyone" only to be applied to airline tickets?

Negotiating a price is as old as humans. "That merchant over there is charging 10% less. Can you beat that?", "I want to buy 10 of these, can you give me a bulk discount?"

I have friends that haggle at local stores. One goes does the "Store X is cheaper thing". Another does "My parents live in Oregon where they're is no sales tax, can you lower your price to cover the difference? Otherwise I'll just have them bring it down from Oregon", etc....