In a given action, the person chooses the amount of a good that he believes is suitable to the attainment of his end. That amount we call the “unit of the good.” So, in your example, the unit of money is $1,000. If your vacation was the highest-valued use of $1,000 for you and you had another end that could also be satisfied with $1,000, then the second unit of $1,000 would be less highly ranked by you than the first unit of $1,000.
