The below Calculator gives an approximation on heats and revenue based around Solo tickets only (Pairs are more and therefore revenue will increase so this is worst case scenario) and utilising 1 Full lane of equipment as an emergency lane. The below figure would be the gym earnings minus half of the costs as shown below:

The deductables (split between Driathlon / Hosts) are as follows:-
Judges T-shirts
Certificates
Scorecards
Finisher Patches
Branding Banner
Approximate costs on average around £70-100