Your card gets an authorization hold through Stripe. The money never moves into anyone's account, including ours, until the minimum is hit.
Join at $1,671 and the group hits 25? You get billed $1,519. The tier you joined at is a ceiling, never a floor.
If the buy does not reach 10 kits by the deadline, every authorization releases automatically. No refund request, no chasing an organizer.