By comparison, China builds above ground high speed rail for about $15M/mile.

Without paying US prevailing market wages to the contractors.

Also, all the materials used on the Hawaii rail line have to be shipped in - literally, adding expense.

You should take a second look at that. Average wages in China are $12k/year, only a third of the US, but higher in the industrial areas, and in terms of purchasing power it has surpassed every other country long ago since everything is so cheap at scale. They have half a billion people in the middle class.

When you are directly comparing how much something cost to build, such as a mile of track, in USD, Purchase Power doesn't matter, does it? This is what the Parent post was asserting.

China builds a mile of track at half the price because they literally pay their people half the price (or less). It doesn't matter that their local Purchase Power might be greater.

Taking it a step further, the Parent was comparing a mile of track in China to a mile of track in Hawaii, which literally has to ship all supplies, and likely a lot of labor, across an ocean. So it's not a great comparison even if we remove labor costs.

Well, if at labour prices at half of the US average China can build high speed trains at a fifth of the price that we can build tunnels, there is more to it than that.

How much does it cost the respective governments for right of way land? Environmental studies?

Right of way of land works in largely the same way in China than in the US. If you have the 99 year lease for urban terrain, or ownership of rural terrain, the government pays you the amount it would cost for you to buy similar land in the case of rural expropriation, or a market rate for your lease. You are also compensated for improvements to your land, such a crops or buildings. In the case of land owned by collectives, the collective is paid for land value but not improvements, which are paid to the farmer.

In practice, laws are not always followed to the letter, but the same can be said in the US. You have the right to appeal to higher court, which is effective as unless it is a hugely major project, expropriations are generally made by the municipal or regional government.

As for environmental studies, they are directly paid for by the government. Environmental standards obviously vary, but have been strongly strengthened in the recent push against pollution.

> It doesn't matter that their local Purchase Power might be greater

It matters because it means that the economies are not directly comparable.

You said they can only do that "without paying US prevailing market wages to the contractors." as if that is somehow an unfair advantage. But if their workers don't need US salaries to have a good living standard, because purchasing power is higher, and are not being exploited, where does the problem actually lie?