The mechanic would have gotten little or no commission if you had bought a bike. He may be a bike snob, but he is not greedy. He works in a bike shop.

Some are just bike geeks, and given that he knows you'll be riding a lot, he'd like to see you on a new bike, because he thinks you'll be happier that way.

There is serious attitude problem at many bike shops, but I'd give this guy the benefit of the doubt.