I haven't thought of pricing, but I'd like to keep it affordable. The hardware module can be configured to permanently bond to the raspberry pi - meaning once the raspberry pi dies, the module is useless (proper HSM).

If not configured to bond, it would be less secure, but depends on what the person wants I guess. Making it bond to the raspberry pi requires that I physically modify the module before I send it out.

The module will run off the replaceable battery and also protects itself from power fluctuations/brownouts, etc. (it slides in whenever needing to be replaced) - and estimate that it will last about 3 years before needing to be replaced.