Shut off the ISK faucets, turn on recirculation pumps.
A lot of hubaloo is given to ISK faucets and sinks, and there is a way to prevent inflation: Stop Printing new ISK.
Step 1: determine how much ISK is needed to be available in the game, put it in a pool, minus the amount already in the wallets of the players.
Step 2: set up a ratio between all faucets to pay out relative to the amount in the pool. As the pool shrinks, so do the payouts, but relative risk/reward stays the same.
Step 3: The pool is replenished by ISK sinks. NPC corp taxes, repair fees, office rentals, etc… all go back into the pool.
Step 4: Wealth Tax. All liquid ISK in all wallets are subject to a continuous interest rate deducted daily. This would be expressed as a percentage, so the more wealth you have, the more holding it in liquid form costs you. This would also go into replenishing the pool. It would affect all wallets, corp or individual, subscribed or not, no exceptions.
I expect that barter will become a thing, as people seek to secure large wealth in the form of goods rather than liquid ISK. Inflation should be fairly quickly reduced, and replaced with more of a flux value as payouts grow and shrink with the pool.