I'm curious about the "if traffic was billed, it wouldn't have happened" part... are you saying that if traffic had been billed per [unit]byte, there would've been no incentive to build fiber networks?
No, if traffic were billed rather than free, we would only get traffic that was deemed to be worth the bill. Most spam, for example, has a very low rate of return. If it cost to send - even a little bit - much of it would become unprofitable.
So in that world, we would have fiber, but not (much) international spam.
The Internet could have worked very differently, with virtual circuits instead of raw datagrams. That's what the telco people wanted. See TP4.[1] Although there's a connectionless TP4 mode, one plan was that you'd only be connectionless within your own organization. If you wanted to talk to the larger world, you'd have to dial up a billed virtual circuit via your telecommunications provider.
Really cheap fiber backbones are make a pure datagram Internet work. We still can't handle congestion in the middle of the network. Congestion has to be forced out to the edges. There was a period in the late 1990s when MAE-EAST and MAE-WEST, the big peering points, routinely went into congestion collapse and only about 30% of packets got through
Ha, not to say too much, but I've been reading a bunch of network history stuff lately as research for a speculative fiction setting where there's no unified TCP/IP spec like we have today. (Although I'm far from an expert on networking in general, lol.) I've read a little bit about OSI and the protocol wars, but the CLNS stuff in that wiki link is totally new to me, so this looks like fertile ground for me. Thanks for sharing!
There was an era of "multiprotocol routers", which routed IP, Xerox Network Architecture, DECnet, and maybe TP4, PARC Universal Protocol, Microsoft Server Message Block, and IBM's SNA. Stanford built those, because they had many incompatible networks internally, and Cisco, being a Stanford spinoff, supported multiple protocols.
This burned a lot of effort in the late 1980s and 1990s. Much incompatibility. Attempts to use intermediate machines to help with protocol conversion. Attempts to build protocol converters. A need for O(N^2) different protocol converters. Some computer vendors had to be dragged, kicking and screaming, away from their proprietary networks. There was a lot of pressure from DoD to standardize.
Down at the wire protocol level, there were alternatives. Too many of them. IBM had Token Ring. Apollo had a different token ring. Datapoint had ARCnet. Industrial automation people liked RS422, which is still around. DEC had a triaxial coax system. ARPANET IMPs had their own strange parallel interface. Ethernet came in two coax forms before un-shielded twisted pair took over, plus a form of Ethernet which connected via a 15-pin D-sub connector. Sometimes you just skipped the Ethernet cable and plugged all the 15-pin cables into a multi-port repeater. Plus there were a bunch of photonic links.
Finally, IP won as the only long-haul packet format, RJ45 jacks handled most electrical interconnects, and most things just plugged in and worked.
So in that world, we would have fiber, but not (much) international spam.