+1. When I was a poor student just getting into cycling and not knowing the difference between a Huffy and a Trek Madone, I bought a used department store bike from a friend for fifty bucks. When another friend, the one who eventually got me hooked on cycling, suggested that I should take it for a tune-up, I said it didn't make any sense to me to pay as much for the tune-up as I paid for the whole bike. I am sure many (probably most) owners of bike-shaped objects feel the same way.

As someone who's seen and did work on a fair number of bikes, I certainly know that in many cases cheap department store bikes are often simply unrepairable. I absolutely can understand bike shop mechanics who don't want to work on them. It would take more time and effort, the result often won't be that great no matter how hard you try, and the customer, who thinks bikes are toys and should be cheap, will not like the price tag.