Paying your people jack, pegging your currency, ignoring other environmental concerns (re mining and processing minerals), nationalising out competition in infrastructure that would have otherwise put the price up...

But no, it's probably just coal's fault.

Edit: I'm not saying that it's not a factor but it's one in a vast array. A country that can unnaturally and immorally suppress its workers and environmental goals will always manage to produce for less money.

The real problem is we let things get this way. We ignored allowed open trade. We don't fix it by going back to coal, we fix it by forcing China —and its spiritual successors— off it.