True!
I think the problem for the WJ Jeep diesels was it was always a diesel conversion for the export market with limited sales numbers compared to the home market where I6 and V8 petrol's ruled!
You had the 3.1 VM Italian diesel for the first 18 months then they put the 2.7 CRD Merc in as Daimler AG didn't want VM when they bought Chrysler in about 1999, so they dont want to be holding parts for competitors engines, they put the prices up on the VM parts to encourage owners to not bother asking for them and maybe sell and buy a newer car with their engine in.
You now have the same problem again as Jeep are now owned by FIAT who also own VM so don't want to be holding parts for Daimler AG engines, so put the price up to £140 for a simple radiator hose!
I am thinking of buying a WK at some point but will be deferentially getting the V8 petrol even if I have to put up with the SRT8
to avoid the problems you're having finding parts for the diesel model WJ.