Sometimes core charges are expensive when a car was recently introduced. That is another time when cores are hard to find.
I remember needing rebuilt calipers for one of the earliest Sprinter vans in the USA. There was a long wait, high core charge, and a very high price for the part. Few cars in the junkyard, few cars with early failures, and a low failure rate were causes.
This happened to my mother back in the late 1980s. She had a 1985 Nissan Maxima, and there were no rebuilt racks anywhere. She could only get one brand new, and got stuck with $1200 parts and labor.
High core charges and prices were common back in the 1980s. That was because there were few CV axle rebuilders, few good cores, and CV axles were absolutely horrible back then. A/C compressor core charges sucked too, as there were so many different types.
There are low core charges and low prices for common vehicles, and the biggest example I remember was a 1980s Ford F150. A front caliper from Pep boys was $35, and the core charge was $5!