Thanks, @greve! Had a break to take, pardon.
Transaction-based payments should eliminate the big concern that I feel about the implementation. Just personally speaking, it’s a rare case that I will sign up for a monthly fee for anything - unless I’m feeling a dramatic benefit inherent in the service. Perhaps when the full-up program is running in my Gmail, I’ll understand.
Simplicity is crucial, agreed. Just throwin’ out ideas. 
Good luck! Hopin’ this goes through the proverbial roof on the way to the moon.