I personally find the way the Devs have set payouts inconsistent and strange (for any server), so had an idea for making it a lot more consistent for a reasonable payout per mission. Now this is just an idea, so if anyone has improvements, please say them.
This is a rough generalised idea, with payout being per vehicle that is required on the mission
200c per basic fire truck
300c per Aerial Platform
500c per specialist appliance (Rescue/Hazmat, etc)
600c per support vehicle
700c per Mobile Command Vehicle
Again this is just a rough idea