Hm... not sure how long we'll keep it up. The discount is a promotion, but I imagine we'll keep it in some form as marketing for the product. 10% is a nice number, but we'll test it. As pointed out in other comments, it beats Starbucks's own program, which I like.
We can afford the discount by saving money elsewhere. No credit card fees, etc.
We can afford the discount by saving money elsewhere. No credit card fees, etc.