well there are a few things needed to make this fleet profitable. First of all as your fleet grows the enemy pirate bounty fleets grow as well, as the enemy pirate fleets grow as does the price on their head.
I'm currently looking at bounties of around 260,000 before additional in-system faction bounties on any enemies. You can easily earn about 350,000 for a single target fleet - this more than covers loss of a few frigates and destroyer etc. that you incur during the fight and need to replace. It also covers fuel, supples, repairs and tarrifs. It still stings when I get pinged by a patrol, but I can absorb that loss as well.
The other thing is to keep on moving from system to system, lawn mowing the profitable bounties. You don't stop to dawdle or take in the sights, you are an industrial scale murder machine - production cannot stop for long. You repair, refuel then head off to another system.
To maintain a high CR for repeated deployments you need to retain highly trained crew, in which case I often use hull/armor/bulkhead mods to reduce loss of well trained crew.