Once I was talking with one of my managers about the saying. She too concluded that it wasn't always right; instead, she opted for the more vague (yet more truthful) "the customer is always first." Generalness and fluffiness aside, I like this a lot better.
Case in point: working in a coffee shop. The highlight of my job very well may be when customers mispronounce the names of drinks. Apparently we once had a customer who asked for a large mocha. The "ch" was where she got into trouble; she pronounced it ch as in cheese rather than ch as in chameleon.
I always thought that the joke about a guy asking for a large fa-jigh-ta was just a joke, but apparently I was mistaken.