China tends to be pretty opaque about a lot of details. They just don't have the same degree of navel-gazing narcissism that leads them to put everything out on the web in searchable English that the USA has.

Undoubtedly there are lots of statistics on this, but they are in Mandarin in governmental and industry reports meant to be read by other Chinese speakers inside China to help them adjust and align. That's behind the Chinese Fire Wall, so Google doesn't even index the majority of them.

I haven't run across a report by bi-lingual analysts or researchers specifying the costs, so I've had to rely on western market prices for Chinese heavy vehicles, which is anecdotal.