I,ve often thought about it in GP races or the last 4 races on the programme where prices are superior but frankly never used it on any race.
One could perhaps reverse the price ratio to have $15 on the 3rd fav etc

I have about 600 commercial systems collected over the years and occasionally put one up for consideration.
There were some reasonable ideas amongst some of them but in the long run most left me poorer but wiser.

Cheers.
darky.