Consumers should have an option. Accept the replacement value or the manufacturer has to repair or replace the unit at their cost. If manufacturers want to try to source a million used dehumidifiers that don’t have this problem, they should go for it. Don’t dump that responsibility on consumers though.
I suspect though that a unit that retails for $100 costs them $25-$35. It would be cheaper to just replace all of them with new ones.
If the “worn out dehumidifier” was a fire risk the whole time, the manufacturer should consider themselves lucky if they get away with just providing the cost of a replacement now.