Depends on willingness to pay - Even if your cost per customer is 0 maximising profit would mean that it’s better (for you) to sell 10 licences for £1,000,000 a pop to rich customers who really need the service rather than 500,000 licences for £1. It’s a shame because those 500,000 miss out on your product even though it would cost you nothing if they were to use it. This is where price segmentation comes into play - maybe you can still charge those 10 big customers the full whack, while providing benefit to the 500,000.