Always ask for examples of work, and perhaps share with us here. There are a few people on here that really know their stuff in regards to seo and other stuff beyond just a good looking site.
I know for a fact that website pricing is a lot like lawn care pricing. Their are going to be people that claim they can produce a site for $299-1000, Just as some will mow a lawn for $20 that I have gotten $45 for 3 years in a row. Difference is going to be quality, in some form or another.