This is difficult to answer and a question that is frequently asked. The biggest factor here is how much time and effort you are prepared to put into your race night to make it a massive success. Here is a rough idea on what you could make with 10 race night customers:
Race night sponsor for each race
8 x £10 = £80
Race night admission tickets sales
10 x £1 = £10
Sales of Racenight horses (8 races x 8 horses x £1)
Betting on each race
10 x 8 x 0.5 = £40
Total Income from just 10 customers
This is just roughly based on 10 clients . Just goes to show you can make money with not many customers.
The most essential thing to remember with any race night is to try to get as many people to your event a possible.
Good luck with your event!