They're only going for 51 orbital planes and it's fairly simple to spread out many satellites from a single launch if they're in the same orbital plane. And a Falcon 9 can carry 20,000 kg to orbit whereas each satellite is pretty light. Some people on /r/spacex calculated that the binding constraint is actually the volume of the Falcon 9 payload fairing and they'll be able to launch 20-25 satellites at a go. And I would expect that mass produced satellites to be far cheaper on the margin than bespoke ones. All of which is to say that it's probably more like $10 million per satellite launched.