> people vocally want certain things (eg. prevailing wages) more than they want efficient costs so there's little incentive to make things cheaper

If you look the database they linked you'll see that there's no correlation at all with GDP/capita and $/km of rail line built. Some of the most efficient on costs are countries like Finland, Korea, Spain, Switzerland, It's clearly not all about the wages.

https://transitcosts.com/new-data/