The price comparison is a bit disingenuous IMHO: coffee is $3 only if you buy a latte at Starbucks. Homemade coffee is probably less than a tenth of that even if you use capsules, and a filter coffee can be as cheap as $1.
You can also buy 20 g of caffeine in pills on amazon for around $8 compared to your 7.2 g for $15.
Why would you compare with something that is effectively the cost of sitting down for half an hour in a clean warm place with toilets and internet? (I'm assuming the cost of actual coffee at starbucks is negligible)