Is it cheaper to build here, or there?

Labour cost, how much of the material basket has to be imported, and what the building code requires. The third is the one people forget: an insulation requirement, a seismic band or a frost depth adds real elements to the building, not just a percentage to the rate.

Because 200 countries produce nearly 20,000 possible pairings, and almost all of them are combinations nobody searches for. Comparisons are published against the markets people actually benchmark against, which keeps every published page one somebody wants.

No. They are order-of-magnitude benchmarks for comparing markets, in USD for comparability, covering construction cost only. For a real number, measure your own drawings in the market you are building in.

Rarely without change. Beyond the code differences — foundations, seismic, wind, insulation — the two markets usually measure bills of quantities to different standards, so the bill has to be re-measured before local contractors will price it competitively.