Inflatable PFD rearm kits typically consist of:
1 – CO2 cartridge
1 – salt packed bobbin
1 – green plastic indicator clip

The wholesale cost of a 24-38oz CO2 cartridge is less than $1 in quantities (search Alibaba).
The mfg cost of bobbin can’t be more than $1 in quantities.
An injection molded plastic clip can’t be more than a few pennies to manufacture.

The point is that the markup for rearming parts/kits is mind boggling. Rearm kits should be retailing in the $10 ballpark, not $20-$40. After a decade of being on the market, the initial inflatable PFD R&D bubble should be paid off. One can observe ample competition in inflator devices (Halkey-Roberts, United Moulders, Hammar, Chinese off-brands) as well as jacket-bladder vendors (Mustang, Onyx, et-al). The only thing I can surmise is the liability ‘insurance’ in the PFD industry must be astronomical.