question:  Why did Harvey agree to pay the absurd price for the water that he and Joe consumed at the bar?
context: When Harvey staggered pontifically into the battered metalloy saloon—the only one on Planetoid 42—his tall, gangling partner was already stumbling out, mouthing something incoherent. 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. Our condenser broke down, and we've gone without water for five ghastly days." Water's five buckos a glass. 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." "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. "Now do you see, my hot-tempered colleague?" said Harvey as he and Joe picked up buckets that hung on the tank. "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. "You don't need any more," said Harvey, dismayed. Harvey studied it worriedly, put his own hand somewhere on it, swallowed as it closed, then breathed again when his fingers were released in five units instead of a single compressed one.
output:  He knew they would be able to con Johnson right back.
options:  The sheriff had threated them with his holstered weapon.  He knew they would be able to con Johnson right back.  They were thirsty and too delirious to argue  He didn't want to risk being arrested and trapped on Planetoid 42