> How did TTC get a monopoly in the first place? All of that capital raising and infrastructure building would have been noticed by other people in the economy and attracted competition well before there was 100% market penetration.

In reality when it comes to telecom markets, many of the big ones were granted monopoly rights.  I still believe it could have worked out without government intervention - maybe not at the biggest scales, but still ... if one company would start with telephone lines while everyone else are using horses for message delivery, one can get quite a competitive edge.  It's of course risk taking at its fines level ... one can say that people should be rewarded for taking risks, but it is harmful for the society that one company has such a big grip on the market decades later.

If TCC would be starting i.e. in City of London, expanding to Westminster and so forth ... even if another company starts in another borough of London, the TCC could gain such an upper hand that they could gradually overtake customers from the competitors or buy up the competitors, becoming the de-facto monopolist in all UK.  Fully possible I think ... but it's quite hypothetical.

Microsoft, Facebook and Google are the bigger elephants in the room, internationally.

> So if we grant that those costs were not heavily influenced by various other legislation (they were), then you have something near a monopoly for a small geographic region.

> But then what? If the quarry used their monopoly power to the point where it made sense for a consumer to ship in gravel from farther away then the quarry would be losing business. So even in that case there was some competitive pressure to keep prices lower than monopoly theory would suggest.

That's pretty much what I said - the price limit for what the "monopolist" can charge is limited by the alternatives, in this case the price for shipping in gravel from quarrels further away, not by the actual cost of production.  Now if it doesn't cost too much shipping in gravel from quarrels further away, it doesn't matter that much for the end consumer anyway.

On a related note, I've heard quite some Russian fishing boats unload their cargo in Tromsø, Norway and ships the load by trucks through Finland to Moscow rather than by rails from Murmansk because the harbour fees in Murmansk are too high.

> In the tech space the landscape is littered with IP laws and lawsuits. It's a freer market than most simply because of the pace of innovation, but we can see in the crypto space with its generally open source software that we get a lot more variety a lot faster without artificial barriers to entry.

The network effect is still very strong.  Consider Bitcoin, it historically had some 80-95% market share of all cryptos according to coinmarketcap, all until they got into capacity problems.  Even though it's open source, it's heavily centralized both at the mining side and the development side.