Agreed. The analogy also breaks down quickly because there is no car dealer that sells both a 10-year old Ford and F1 McLaren. Generally, dealerships offer very narrow bands of value within that large range.
Don't be a used-car web dev then. Be the luxury sedan - sport car web dev. I explain to my clients (not necessarily through this analogy) that I'm definitely not the cheapest dev/designer they'll be able to find, but that they'll gain more quality, etc. for more money with me (with case studies to back that claim up). I don't sell my clients used cars, and so they don't expect to pay used-car rates with me ;)
