Niall
The fees are based on different promotional pamphlets I've seen from Fowler & Simpson; Colt, Mackenzie & Alison and Mackenzie. In the early 20s their fees were based on a sliding percentage of the overall cost of the project (6% to 10% plus expenses). By the mid to late 20s Mackenzie was charging $2000 for a new course and $200 a hole for a redesign (plus expenses), based on the rate structure of the Society. Colt & Alison charged Tokyo GC £1500 plus expenses. £25 in 1923 would not get you a new design or a major redesign.
By the way there is a chapter devoted to golf architecture in Darwin's biography of Braid. In that chapter there is a long list of Braid's major designs/redesigns and neither Brora or Pennard are included.
Some of Watson's more prominent designs: Minikahda, Interlachen, Ravisloe, Homewood (Flossmoor), Thousand Island, White Bear Yacht, Olympia Fields (2 courses), Annandale, Hillcrest, Flintridge, San Diego, California, Ft. Washington, Olympic (2 courses), Harding Park, and Belvedere.
Hutchison: West Sussex (w/Campbell), Ashridge, (w/Campbell), Sundridge Park (w/Campbell), Brancaster (redesign), North Berwick (redesign), Pitlochry, Wimereux, Gleneagles (2 courses w/ Braid), Seacroft (w/Campbell), Leeds Castle (w/Campbell), Kington, Woodhall Spa (redesign w/Hotchkin), Turnberry-Old (redesign), Deal (redesign) and perhaps his most spectacular design (w/Campbell) was never built, St. Andrews-Modern.