 How does Johnson trick the duo into paying for things more than once?
In their hectic voyages from planet to planet, the pair of panacea purveyors had encountered the usual strange life-forms. Paying no attention to them, it was carrying a case of liquor in two hands, six siphons in two others, and a broom and dustpan in the remaining pair. The interplanetary con-men drank noisily, asked for more, until they had drunk eight glasses. Meanwhile, the bartender had taken out eight jiggers and filled them with whiskey. Our condenser broke down, and we've gone without water for five ghastly days." Liquor's free with every chaser." "When there ain't many customers, you gotta make more on each one. It's bitter as some kinds of sin before it's purified. "Friend," said Harvey, taking out a wallet and counting off eight five-bucko bills, "here is your money. What's fair is fair, and you have put a different complexion on what seemed at first to be an unconscionable interjection of a middleman between Nature and man's thirst." "On account of the quantity, I'm able to quote a bargain price. Shucks, boys, it hurts me more to charge for water than it does for you to pay. The planetoid man worked the pump while the mayor intently watched the crude level-gauge, crying "Stop!" when it registered the proper amount. Then Johnson rubbed his thumb on his index finger and wetted his lips expectantly.
 He is dishonest. He offers something for free, without mentioning the actual price of it or that there even is a price.
 He strong arms them into buying with his son.  He is dishonest. He offers something for free, without mentioning the actual price of it or that there even is a price.  He takes advantage of their good will.  He doesn't trick anyone - he is an honest man that is running several jobs.