Is expiation required for one who swore not to pay more than 10 dinars, but then paid the full amount?

There is no blame upon you for doing what is better, and you are obliged to offer expiation for your oath, based on the saying of the Messenger of Allah, may Allah bless him and grant him peace: "Whoever takes an oath and then sees something else as better than it, let him do that which is better and expiate for his oath."