How big is this $15 bag of coffee that you finish in a week? Here in New Zealand a standard 200g bag of beans from a good roastery is no more than $10 NZD, about $6 USD.
San Francisco and the Bay Area will also easily charge $20 for sometimes even just 12 ounces of beans. Pretty wild, but IMHO San Francisco has some of the best cafes, baristas, and actual drinks. I moved to Southern California and it's still good and they charge almost as much too but still not as good.
In my area, the cheaper end of quality beans is roughly $1/1oz, so 200g would be $7 (Though, I find beans are usually sold 12oz (340g) per package). Personally, a 12oz bag last me roughly 2 weeks, but I only drink 1 cup per day.
maybe 12oz, but this is high quality, not at all like the stuff you would get in Wellington