I'm sure Norinco would love to sell the better (and more expensive) stuff in, but the PLAGF looks at the price tag and goes "lol nope."
In my humble opinion, strict price control is the main beauty of this vehicle. Selling point of those vehicles is maximum bang for the buck, and not a single rmb over that.
Just two examples:
1, wheeled koalitsiya. Extremely expensive turret(Russia intends to keep Msta in production!) on a (censored) chassis.
Unarmoured, overloaded and outright unstable. Pantsirs on same base overturned multiple times on wet highways. Now imagine escaping return fire on this.
2, Malva. Right kind of gun mount, and a good, special, armoured base. Really good base. The only problem, is this base
alone drives cost to near-SPH levels for something that was intended to be a gun bolted to its tractor unit.
Small armies may buy whatever they want, but for larger forces -best is an enemy of the good enough.