Dont know if this is a Gross box,but given the amount of work it takes to do one,and the acquisition price of a core,his pricing is good.
1. extend the steering shaft.
2. machine sector shaft.
3. adapt bearing end cap for light rod.
plus cleaning up the core and doing what it needs.you can do it yourself,but in the end if you add it up and value your labor much you'll see he offers an honest product at a fair price.