Yes, but hydrogen-air is already cheaper than that. On large scales it is <$1/kWh and easily cheaper than anything can even theoretically attain.
If so, the metal-air systems have a major advantage on the discharging side of things by avoiding the need of a fuel cell and being able to harvest electrons directly via galvanic current.
The galvanic discharge rate is extremely slow and not really suitable as part of a rechargeable battery system. Any practical metal-air will have some way of discharging faster. The problem is that we have basically solved this for hydrogen-air but not for anything else.