People say it's impossible to negotiate prices at modern grocery chains. They only had brand name lactose supplements. The manager gave me a hard time about it, I asked about a price matching policy, shrugged, and let me pay the generic price. I'm sharing this anecdote because I don't think people try hard enough and you might be surprised if you do. You won't win every time, but try asserting some authority.

By assuming markets are so rigged against you, it discourages people from even trying. Price discovery can only happen if you attempt to be firm. If you'll roll over instantly, then sure, they can do as they wish.