I suspect JTK has not quoted the letter precisely.I would, but it would be pointless, because it's essentially the same question I had, and I don't know the answer. If the vehicle's value is declining, then the replacement cost must also be declining, and the cost of repair would be constant or slightly depressed as good wrecker's yard parts become more available. So how can replacement cost be a greater portion of the premium as Monnex told jtk?
Here's the only scenario where I can imagine that wouldn't be true: That you did a deal where 'replacement' was actually a brand new version of the old beater that got totalled. But I can't see that as being reasonable deal for customer or company beyond maybe the first year or two.
Surely it would be obvious you'd do better to depreciate your own car and have that money in the bank instead of asking the insurance company to build that into the premiums and seeing it disappear if you drove safe. They'd have to bank more and more against that nasty possibility every year hoping you'd not notice and pay up until … Wait a minute!
Is that it?
Replacement costs arn't a stand alone premium category. Collision is.
While I don't know what model of vehicle is involved, but if a lot of them were in crashes for a the prior rating period, or their parts cost went up, or repair rates were renegotiated, the collision factor can go up.
But considering that collision does not make up a significant part of the premium dollar, a 30% increase is just about mathematically impossible based on collision alone.
you should also be aware that insurers will not authorize repair facilities to use "wrecking yard parts" to repair your car.