 Why does Joseph lie about the water supply?
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. Through thirst-cracked lips he rasped: "Water—quick!" The interplanetary con-men drank noisily, asked for more, until they had drunk eight glasses. Medical science is unanimous in proclaiming this magic medicine the sole panacea in the entire history of therapeutics." Our condenser broke down, and we've gone without water for five ghastly days." He came near starving and moved on to Titan. It's bitter as some kinds of sin before it's purified. Waddya think—I was chargin' feller critters for water just out of devilment? 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." "And chief of police, no doubt," said Harvey jocosely. "About seventy-five liters, if we go on half rations," he answered. "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 asked: "But what are we to do about replenishing our battery fluid? "Now do you see, my hot-tempered colleague?" said Harvey as he and Joe picked up buckets that hung on the tank. "Johnson, as I saw instantly, is the victim of a difficult environment, and must charge accordingly." "Just the same," Joe griped, "paying for water isn't something you can get used to in ten minutes." In the fragile forest, they soon came across a stream that sprang from the igneous soil and splashed into the small pond whose contents, according to the mayor, was theirs for the asking. They filled their buckets and hauled them to the ship, then returned for more. It was on the sixth trip that Joe caught a glimpse of Jupiter-shine on a bright surface off to the left. "It leads to the saloon," said Harvey, his eyes rapidly tracing the pipe back toward the spaceport.
 He wants people to believe they need to pay for it.
 There isn't a lot of water there, and he needs to be able to ration it out.  He wants people to believe they need to pay for it.  He wants to keep the fresh water for himself.  He thinks that people would prefer to buy filtered water.