You're using "value" for "utility". The "value" of the network is how much people are willing to pay for it. They don't pay because it's valuable. It's valuable because people are willing to pay.

Whenever two parties enter into a reasoned voluntary trade, it is because each values what they are getting more than what they are giving up. To the network owner, the value of the network is what you're being paid. To the network user, the value of the network is what you'd have been willing to pay if you were forced. Those two numbers tend to be different, often substantially so. Vendors would like the gap to be small, and customers want it large.

Metcalfe's Law is about the value that customers perceive, not what vendors get.

In general in a competitive market, the gap tends to be fairly large (in fact economics says that the price should be the marginal cost of the last provider). In a monopoly the gap tends to be much smaller. If Metcalfe's Law holds, then a vendor should be able to dominate a market, and then proceed to jack up prices substantially, trusting to network effects to keep competitors from getting established. So the market should tend towards a monopoly that eventually becomes very profitable.

This plan doesn't seem to work as well in practice as Metcalfe's Law would predict.

As for your comment about where we should use Zipf's law vs Metcalfe's, we didn't use either. We used our own n log(n) law instead. As for whether to use a variation, while it is possible that the smaller network has all of the value, it is highly unlikely in practice. If you disagree, I'd be interested in hearing about specific examples.

Cheers,
Ben