You don't have to take my word for it. There's recently been a push for expansion of Romania's broadband network to more rural areas. At an investment of about $110 million US, it will reach an expected 150,000 additional households, for a cost around $730 per household. Compare that to the US, where the estimate is closer to $3000 and as high as $8000 per household, a 7 to 11 fold increase over Romania. [0]
Nearly all aspects of infrastructure build out are heavily weighted towards labor costs. A 2009 rule in the US required large projects use union labor, and just that marginal increase in labor costs increased infrastructure costs by around 15%. Anecdotally, I had a home addition some years back. Materials costs about 20%, labor about 80%.
Also once built, the capital expenditures for something like broadband drop to negligible rates while the labor cost of maintenance & administration just keeps on going, maybe not as high as the initial build but you need new & different workers too-- sales reps, account managers, etc. Given that prices tend towards the marginal cost of production over time, in this case being mostly labor, it makes perfect sense that a country with 1/8 the labor costs could offer a service at 1/5 the cost in the US, the difference in those proportions accounting for the marginal capital costs of maintenance.
[0] https://www.telegeography.com/products/commsupdate/articles/...