I find it interesting how often there really isn't anything that compels someone to choose one vendor over another. Sometimes it's simply because they just want to "get it done" and you are the supplier they found first, sometimes just because something about your offerings "catches their fancy" over what your competitors offer even though you charge more for essentially the same product or service.
Sure there are the "soccer moms" who shop around for penny savings, but almost none of my customers seem to have the time or inclination to try to pit one vendor against another (and those that do, I just send elsewhere because I don't care to deal with them).
When I started engraving, I decided what I wanted to offer, set my prices at the lower end of the scale, and worked a lot on promotion and exposure. However, over time, I've pretty much reversed all that and business has skyrocketed over last year. Now I do almost no promotion work, customer demand has re-shaped my offerings, and I periodically compare my own prices and offerings against others' and try to stay on the higher end (but not most expensive) with some distinguishing (and, hopefully, compelling) design and presentation differences to motivate those who are doing a bit of comparing to pay the extra I charge, and those who are simply looking for cheapest price to go elsewhere and not take up my time. I am rather surprised but fortunate enough to get pretty much all the work I can handle (more, actually, eating into evenings and weekends at times) at above-average rates I'm happy with, for services my customers are happy with.