What's the best alcoholic beverage in terms of bang for the buck?

I know a lot of down-and-out street people go for fortified wines like Thunderbird and MD 20/20 But do those provide the highest dose of alcohol for the dollar spent? Compass Gin (or 190 proof grain alcohol) is fairly expensive, but you could mix it with grape juice and make a lot of bottles of MD 20/20. Has anyone done the math to figure our which libation winos really should save up to buy?