Does necessity permit engaging in usury just once?

The principle of "necessities permit the forbidden" is agreed upon, and its evidence is the Almighty's saying: "And He has detailed for you what He has forbidden you, except that to which you are compelled." Necessity is reaching the point of perishing or being close to it if one does not consume the forbidden item, and this permits consuming the forbidden. As for need, it does not permit the forbidden; it is like exertion and hardship without perishing. And necessity must be estimated according to its measure, so one consumes from the forbidden only what repels the necessity.