No, the customer is not always right. Most retailers say it anyway, even when the customer is dead wrong. It's why the associate at the returns counter keeps smiling politely while a couple argues over a receipt: the smile costs less than the fight.
But the returns counter is not where being wrong costs you money. The expensive lies happen during the sale, when shoppers hide what they actually need.
They'll tell you they have no need right after describing their need. They'll tell you they have no money while holding a phone that costs more than your best item. Anybody who has worked a sales floor knows it.
Here's the part that matters: they're in your store.
People who have no need don't drive to a store that sells the solution.
People who have no money don't go shopping.
They probably started their search online and already know roughly what your merchandise costs. The words "no need" and "no money" are the two oldest tools shoppers use to push a salesperson away, and the reason they use them is they don't trust you yet.
So don't believe the first no. When somebody says "I don't have the money for it," a good salesperson can ask, "If this took that problem away for you, would you take it home today?"
And you'll hear, "Well, yeah, maybe I would." Now you're back in a real conversation about the problem, not a fake one about the wallet.
The best salespeople push past those first defenses, usually with some humor and always with respect, because they understand what the lie actually is: a trust test.
Fail it by taking the excuse at face value and you validate the customer's decision to keep their guard up. Pass it by staying curious and you earn the honest conversation that was available the whole time.
The customer isn't always right. But they're always telling you something. "No money" usually means "you haven't shown me why yet."