If his dad fixed it, it's unlikely it was a difficult job. And his not knowing how the dangly thing should work hardly indicates derailer repair is necessary. (Unless his not-knowing equates to an opportunity to squeeze him for money. I certainly hope that was not your implication.)

To a newbie, reinstalling a rear wheel can be daunting. To a bike shop mechanic it should be simple. I just don't like the "I don't even look at it for less than 8 bucks" approach.

And maybe you bike shop owners and workers who do take that attitude should list your shop names so we can all know who to avoid.

I have several local shops I frequent. They all are great about these things. I recommend them to everyone who asks and send in lots of bike business, and I spend all my big ticket money with them (auto bike racks, shoes, pedals, seats, helmets, clothes, and everything else I don't want to buy used from ebay or order on line).

Why is it so tough to be decent to people. If you think that threatens your business then you should already know one of your problems.