Coffee beans costs about $10 for 250 grams. That's 4 cents a gram. Apparently one shot of coffee is about 7 grams of ground beans, so the average shot is about 28 cents worth of coffee.
Really expensive Earl Grey tea from T2 costs $22 for 250 grams, or 8.8 cents a gram. But you only need 2 grams per cup of tea, so a cup of delicious tea costs only 18 cents.
Conclusion: drink tea!
(Numbers obtained from the Internet and Kevin, a self-confessed coffee addict.)