Maximizing the revenue from selling two or more goods has been shown to require the use of $nonmonotonic$ mechanisms, where a higher-valuation buyer may pay less than a lower-valuation one. Here we show that the restriction to $monotonic$ mechanisms may not just lower the revenue, but may in fact yield only a $negligible$ $fraction$ of the maximal revenue; more precisely, the revenue from monotonic mechanisms is no more than k times the simple revenue obtainable by selling the goods separately, or bundled (where k is the number of goods), whereas the maximal revenue may be arbitrarily larger. We then study the class of monotonic mechanisms and its subclass of allocation-monotonic mechanisms, and obtain useful characterizations and revenue bounds.

翻译：将销售两个或更多货物所得收入最大化,证明需要使用无价机制,高估买方可能支付低于低价机制的价钱。 我们在这里表明,对美元机制的限制不仅可能降低收入,而且实际上可能只产生最高收入中可忽略的美元;更确切地说,单调机制所得收入不超过通过分别出售货物或捆绑(在K是货物数量的情况下)获得的简单收入的千倍,而最高收入则可能任意增加。 然后我们研究单调机制的类别及其分级分配-通量机制,并获得有用的定性和收入界限。