I think the Ozracingtools Racing Ratings to Price spreadsheet has its limitations.

I entered a fictious 10 horse field using Unitab ratings (80,82,87,88,89,90,97,98,99,100) and the odds spread was $9.50 for the top 4 rated, $10.50 for the next 4 rated and $11.50 for the last 2 rated horses. This is obviously meaningless if you are trying to set a price for each horse using these ratings. The same effect is shown for Zipform Rating figures e.g 52 through to 62.

Not sure what set of rating figures would work.