I’ve seen the classic ‘Oh, you’ll need to buy XYZ product’ line given to noob customers numerous times. Bike shops (chain and local) seem to make a lot of dishonest money this way.
I mangled a rear mech a few years ago, and the nearby chain store didn’t have the jockey wheel and pin that would have fixed it. Instead they told me I could buy a whole new mech and they’d fit it for about £60. I walked home, and they got nothing. Stocking the bit I needed couldn’t have been too difficult, could it?
To be fair, the guy in the shop was helpful and friendly, and lent me a chain breaker from the workshop, which he didn’t have to do.