> I can't relate to v/mV
A different way to express gain, in a way that once was practical. 1mV at the input makes 200V at the output. Gain is then 200V/1mV= 200,000:1. Saying 50V/mV actually made sense in vacuum tube op-amps, and the custom persisted until sand-state opamps grew to absurd gain.
BUT: what use is knowing that? Because this is surely a DC gain. That is (marginally) useful in low-speed DC analog computers. And it has "Wow!" factor. But knowing a little about opamps, I expect that gain starts to fall by 100Hz, and may be less than 20V/mV or 20,000:1 in the middle of the audio band, less than 1V/mV or 1,000:1 in the top of the audio band.
In audio, Gain Bandwidth Product is important, DC gain normally is of little or no interest for the usual opamp designs and compensations.