Nigel, I just got an email from Alembic stating the following: The kit is $65. It's a switch that's prewired with a radial capacitor
(nicely skrink tubed, of course) and some copper shielding tape. Instructions are included for you to remove a box cap from the filter board, and for drilling/shielding the hole to mount the switch.
Sounds like a good deal to me!