Just a wild guess. I imagine that Jeff does not do the casting in house. I imagine that the company that does the casting has a production minimum before they pour.
Just call some casting companies in your area and see if they can do a one-off casting to your blue print and see how they price it. Then take your raw casting to a machine shop, with your blue print, and have it machined. Not to mention that a lot of castings get "seasoned" for days/weeks/months before they are machined. It is not hard to understand how it might take some time to get your hands on such a specialty item from the time the order is placed.
Just speculation on my part. Of the products that I have used/know people that have used, his products are worth the wait.