My own tried and tested formula for determining if prices are getting out of hand is how much of an, erm, “rounding error” occurs when relaying the price I’ve paid for something to the wife.
When it comes to cameras, it would be a base level of 10%.
If I bought a new camera nowadays it would more likely be in the 20-25% area.
The area where my perception of price escalation is most piqued though is in the price of first party lenses as much as it is cameras.