Great question but nearly impossible to answer as people do not tell the cashier why they are buying coffee. That said, there are a variety of ways to measure a sales bump or put value on what it is worth for each person who views a Starbucks advertisement. Given the quantity of people reading and reposting Starbucks logos along with Game of Thrones screenshots on social media over the last few days alone the value would be around $2 Million. Over the next week it may gain another million dollars in value before it is no longer newsworthy.