If I was being fitted or having a stock made to my dimensions by someone else I would expect the job be in the 2-3k range. I know others will always seem to have someone who can do it for much less but my luck is never that good. That's why I learned to do as much myself as I can.
The custom measurements do not increase cost as much as you think. It is the total number of hours involved in making, checkering and finishing a stock. The cost of the blank often becomes a minor part of the fee. The cost of making a pattern stock and getting it duplicated has to be added in. After that hours of fitting. It all adds up and good stockers tend to be in demand so you may have a backlog if work to wait behind.