I don't know if you're familiar with the price of those stamina drinks or not. A very popular one, Ripobitan D, usually retails for about 148 yen per bottle in convenience stores. Purchased one-at-a-time, that would come to 310,800 yen with tax. The equivalent amount of caffeine, in pill form, can be ordered for USD23.95. Figure roughly 110 yen per dollar and you're looking at 2,635 yen. It doesn't take a genius to figure out which is the more economical if a caffeine boost is all one is after.
According to
http://www.nsda.org/WhatsIn/caffeinecontent.html a 20oz botle of Mountain Dew provides 92mg of caffeine. We're going to need 1097 bottles of Mountain Dew to equal the amount of caffeine in that 500ct bottle of caffeine pills. Figure 140 yen per bottle and you're looking at about 152,180 yen.
So there are some of the options.
Pay 310,800
Pay 152,180
Or pay 2,635 plus a little bit more for shipping.
It all adds up to the same amount of caffeine buzz, which is all the original poster seems to care about.
I will add that the link I provided was to a firm I have done business with several times and recommend highly for the quality and speed of their service.
So you see, Josh, it's actually more like saying "Why pay for 150 beers when all you have to pay for is one?"