Oxygen - in North Florida a tank is filled for about $4 - $6 and lasts up to ten hours, independent of depth
Diluent - depth dependent, but lasts for a good day of diving for $4
Bailout - these are likely plumbed to your inflator and/or dry suit, but won’t be used for anything beyond safety checks, practice or open circuit bailout, therefore will last up to months prior to refilling unless you have had an incident
Batteries - depends on your unit. Mine is rechargeable, so extremely low cost. My first rig had batteries that were $100 for about 40 hours of use!
Sorb - averages between $25 and $30 per fill or cartridge for most people. These may last from two to six hours depending on your unit, although it is always advisable to start fresh for deep.
Trimix - local prices vary dramatically, but you will likely only need 13 cft (2 liters) of mix for a deep dive. If you keep a filled pair of bailout tanks, you’ll only be refilling the onboard tank for dives. It is cheaper to store an extra set of bailout tanks than fill and dump on a regular basis.
Service - don’t forget to factor service into your life. Don’t wait for something to break. Be proactive. Jill Heinerth