I used to work in a bike shop, which only sold higher quality bikes, no cheap supermarket stuff etc... And so most people who would come in were people with a reasonable income who didn't mind spending a few hundred (or thousand...) quid on their new bike. One day, a chap came in with his son, looking to buy a bike for the wee boys Birthday. So I started chatting to the guy, and he told me he just spent 3k on his new road bike, and that he already had two mountain bikes worth a few grand each. I thought - OK, a kids bike surely won't be a problem then! So I presented him with the selection of kids bikes suitable for his son, ranging in price between £200 - £300. The guy went nuts, said that we must be the most expensive bike shop in Britain (all those prices were RRP's....) and said he saw a kids bike for 70 quid in Asda! For a moment I was speechless, then I wanted to punch him in the face. After I composed myself, I just said that we value the lives of our customer's children and so we don't deal with cheap low quality bikes. The guy didn't have an answer to that and left.....
On the other hand, I experienced loads of nice customers who appreciated the level of service and expertise. Customer service can be sometimes quite stressful, but also very rewarding. It is definitely not a job for everyone tho!