Archbishop of Canterbury John Morton in the late fifteenth century held that someone living modestly must be saving money and, therefore, could afford taxes, whereas someone living extravagantly obviously was rich and, therefore, could afford taxes.
In some instances, such as Morton's original use of the fallacy, it may be that one of the two observations is likely valid, but the other is pure sophistry: evidence of possessing wealth may be genuinely irrelevant to having a source of taxable income.
In other cases, it may be that neither observation may be relied upon to support the conclusion properly. For example, asserting that a person suspected of a crime who is acting nervously must have something to feel guilty about, while a person who acts calmly and confidently must be practiced or skilled at hiding guilt. Either observation therefore has little, if any, probative value, as each could equally be evidence for the opposite conclusion.