Road Infrastructure Costs

One requires expensive road infrastructure, the other doesn't.

Road transport might be cheaper at first, but ongoing construction and maintenance costs do add up in a hurry, and as traffic builds the amount of money that has to be spent scales up pretty quickly.A lot of the savings roads enjoy versus things like rail is that maintenance is perpetually deferred. A private railway has to ensure the tracks are all maintained to a very high standard, to do anything else is to invite disaster, but a local municipality can let its roads go to hell without much

Those links dont support your claim that building a road is cheaper than maintaining it.

*Inexpensive if you don't factor in the costs of building and maintaining roads.

It's not just about road wear. Just installing and maintaining the support infrastructure (traffic lights, road signs, cameras, etc.) and planning the whole system would also count for a big chunk of expenses.

Based on what I've read, it's not that road construction is expensive, it's that ongoing maintenance of roads and connected utilities is quite expensive.

Because roads and pipes cost money, and you eventually have to pay for it.

Over time, most cost of a road is maintenance cost, not initial construction. While this probably isn't linear with use, it does scale with use, so that lower use means lower maintenance cost. The cost of a single lane road supporting current usage levels is not an individual less quantum unit of road cost.

Highways require significant ongoing maintenance - I wouldn’t be surprised to find that the cost of maintenance over the lifetime of the road exceeds the cost to build it in the first place. Particularly if the country in question relies heavily on road freight.

Keep in mind that we don't think this way about roads which are way more expensive and way more money-losing.