It is a common marketing tactic.
A coffee is cheap, most of the times it is less than a dollar, sometimes as low as 10 cents if you brew it yourself from cheap ground beans.
But you probably paid $5-$10 for a coffee on a few occasions too. Though TBH, you may have done it just to rent a seat at Starbucks.
So 1-2 coffees is probably something you correctly value at about $1. By associating it with coffee, they make you think their $10/month service costs you just $1, using the super expensive case as an excuse.