Although this price strategy may be working for you at your shops - likely in coordination will a well run business in many other regards - I'm afraid that as a general rule I must disagree with this approach.
From my experience in working with coffee shops and their customers all around the US, I find that the consumer perception of "cheaper than Starbucks" implies "not as good as" rather than "better value." Setting prices below competition with a mediocre product may in fact be a deterrent for new customers; they expect less.
In this micro-luxury market, I find that loyal consumers are not looking to save a few pennies, they are looking for convenience and consistently good quality. The caveat, of course, is that you must provide a product that is consistently better tasting than the big-named competitor in an atmosphere of comparable cleanliness and convenience.
The "value" crowd is more likely to go to 7/11 for their $.99 32oz hazelnut cafe latte. I recommend that shops will do better financially by attracting the "quality" crowd rather than the bargain shoppers.