The cost of solar is 1X - 20X depending on location. US has the highest costs, followed by maybe Western Europe.
The panels are dirt-cheap[1] straight from China, but your friendly govt adds tariffs.
The balance of the system is super costly in some locations, ridiculously cheap in other locations.
In Pakistan, they are laying out the panels on the roof without any structure.
In most of the third world, homes are concrete built, they already have structural elements and it isn't a big deal to add panels. It is a massive project in US, because of shingled roof. Labor is also available, available immediately, and permitting is either easy or not necessary.
I'd assume the cheapest total install cost would be (cheapest to costliest): China, Pakistan, Bangladesh, middle-east,, Africa, South East Asia, Central America, Mexico, India, South America, Australia, Eastern Europe, Western Europe, Canada, and finally US.
I'm ignoring the cost of land which varies a lot in each country. We also don't need land, just add vertical solar on every structure, fence and wall.
[1]or as cheap as plywood which a HN comment pointed out