What is considered a mina?

It is customary to say jokingly that every matter is a special case for consecrating a woman. Maimonides (Memariam 4:2) says that if a dispute arises over a matter in which fornication is a crime and its omission is a sin, or over a matter “which leads to a matter in which one is liable for fornication and its omission is a sin,” and he gives an example, for example, if several judges disagreed on whether they can rule on the law of money, this is a special case in that if in such a case (which they disagree on whether it is kosher for the law of money) they rule that someone owes someone money and he goes and consecrates a woman with it, then the old man of Mamre will be killed for it.
What is the difference between this and anything that is considered a sin for the consecration of a woman (if it is consecrated on condition, etc.)? In other words, where does the line cross?