Very true.
What works effectively for me is adding 1 to the number of selections and accepting nothing less than that price.
i.e 5 selections in a race I want a minimum of $6.
Over the long term one can never go broke unlike those of the 1 selection per race persuasion.
For me to bet 1 horse per race it would need to be asessed price around $1.30.
In other words generally the price one gets is a massive overlay.
These are few and far between.
1.e Kilcoy R 6 asessed $1.28 Price got was $21
It lost but there are so many that win and adds to the yearly bottom line.

What ever way one chooses it must make sense and suit ones own comfortability and risk.

Cheers