I live on the Upper East Side of NYC. Very affluent neighborhood but i'm not one of them! 2 weeks ago I brought in a carbon fork from nashbar along with headset to have them install since they had the right tools and to watch the process to learn from it. Yesterday I brought in new cranks for them to install and the mechanic says "why you keep buying stuff from the internet instead of buying good stuff from us here?" I looked him dead in his eye and said "I'm not one of these Upper Eastsiders with money, if I was, I wouldn't be fixing up a 27 year old bike, piece by piece. I do my homework, these are cranks that sold brand new 5 years ago for $250 bucks, I got them for $35 but I'm more than happy to pay you guys fair value for your time to install them"

In the end, it works out goodfor all parties. Generally if you buy parts from them, they go ahead and do the install for free barring any major adjustments needing to be done or problems uncovered. Bring your own parts, you get charged labor. either way they make money, I save money and we are happy. Same with bikes direct bikes. They don't mind assembling and giving everything a good once over. Even if they charge $150 for it, I as a consumer can buy a $1000 ultegra equipped bike and pay them $150 for a total cost of $1150 when the cost of a similarly equipped bike in their shop is going to be close to $3000. Even if I have to pay them for a tune up every year, I'd have to get a whole lot of tuneups for it to not save me money.