All the points made here are valid points.
The store could have higher a new person, or may be they had someone else from another department of the store fill in last minute. That to me is perfectly acceptable.

However, regardless of the reason for the lack of correct information from a keyboard sales person, it could be detrimental for the store and the store could be losing potential customers.

For example, if I did not know anything about keyboards and I wanted to get a PSR for someone and went to that store and took the information as the truth, I would have left with out getting a PSR keyboard. And may be the store had PSRs or had the ability to order one for me.

I think some keyboard stores are in a catch 22 situation. They can find a way to get knowledgeable sales persons (and may possibly make them have to increase the price of their products), or they can use the best persons they can afford (knowing that they may not be experts in keyboards, and may occasionally give wrong information to potential customers).

What ever the case, we as consumers must always do research before investing in a musical product regardless of where we are getting it from.