Rickochet So what does the factory do that the tech at Costco didn't do
The factory will make the 'specific to your loss' instruments. The tech can only tweak them. There is probably such a thing as a 'standard' type of loss, frequency loss ranges that are most common, which you must have fallen under when buying & that is why you were able to try them out in store; they probably have them to boost sales and can be adjusted for most people. I'm sure the aids you got are much better than what you walked around the store with. Much more specific to your exact frequency loss(es), and the tech should have made slight mods when you picked them up. If they are digital, that is.
I've had to do without 2-3 times through the years when getting repairs. With my extent of loss, it's a beyotch without one.