Exactly. A good bike should fit one's height and weight like a hand to a glove. And dealer quality bikes will come in different sizes and they will be expertly assembled and tested by shop mechanics for fit, safety and comfort. I have a 55 cm Lemond Zurich. Its a great road bike and new models tend to command a premium price. But if you like to ride the road, its quality build and light weight make riding fun, unlike the experience one encounters with a mass department store "gaspipe" built bike. Ditto for other kinds of bikes, like mountain, cyclocross, singlespeed, folder, BMX and children's bikes.
(Denny Crane: "I Don't Want To Socialize With A Pinko Liberal Democrat Commie. Say What You Like About Republicans. We Stick To Our Convictions. Even When We Know We're Dead Wrong.")