I agree that in its simplest form (which you described), the Law of Supply and Demand is not hard to understand, but, as it true in many things in life, the devil is in the details. For example, there is also the economic concept of elasticity. (Look it up on Wikipedia.) Choosing to cruise on Celebrity regardless of significant recent price hikes indicates inelasticity. Explanations include high disposable income, brand loyalty, pent-up demand, low desirability of alternatives -- and even addictiveness ☺️