I think you need increase MN cost up to 2500 coins but not in one moment and not now.
Rise MN cost on 500 coins every month.
MN owner who wants to keep MN in future will hodl all incoming coins. Thus, you significantly reduce the offer on the exchange.
MN owner will collect 425-450 coins for 30 days and will need for additional 50-75 coins. Thus, you slightly increase the demand on the exchange.
PoW mining must cointinue as you need a source of additional coins.