I haven't had time to look at your spreadsheet but a pretty simple way would be to do something like this:

Add a column called "Favourite"
Write a formula in tat column that gets the Minimum price of all runners, and then compare each runner's price to that. Something like this:
=IF(A1=(MIN(A$1:A$20)),1,0)

Where A1 = the price of the runner
A$1:A$20 is the series of prices of all runners

Put that formula in each cell in the Favourite column. That would put a 1 in the Favourite column if they are the favourite, or a 0 if they are not.