I don't mind hewing on a sawn surface, I think the key to getting it to look "right" is in the scoring.
going price for ash around here is probably 1.00-1.50 bd/ft.
I wouldn't hew for 15/hr unless it was my own stuff.
The outside cuts on a bigger ash log are good stuff in my books, they will cup, but just use them in narrow widths, good handle wood... should be clear of knots.
btw, I think your time analysis on hewing a big ash from the round is pretty good. I had to hew a bunch of 24 ft 6x12 oak joists from the round some years ago, and the time was quite similar. Such a relief to get around to that last side on the big hardwoods.