Donald J. Trump, who has lectured America about architecture, foreign policy and, most of all, how to do deals, may be about to learn a lesson of his own: how to live in Manhattan on $450,000 a month. That scarcely onerous restriction is being imposed by Mr. Trump's bankers, who have insisted that the man who has made conspicuous consumption a personal trademark must curb his spending a bit. Moreover, the $450,000-a-month allowance excludes some of the largest of Mr. Trump's daunting expenses, the bankers say. These extras, based on Mr. Trump's spending in May, include the costs of maintaining his personal 727 jetliner ($246,000) and his 282-foot yacht ($841,000). The yacht and the personal jet, to be sure, may be sold to trim the real estate developer's mountainous debts. In May, Mr. Trump also paid interest of $2.1 million on his personal debt, while his legal, charitable and business expenses totaled $382,000. His interest payments and various expenses do not count as personal spending, either.