When looking for synonyms for the phrase "pay an unreasonable price," there are a number of options to consider. For example, you might use words like "overpay," "spend too much," "shell out needlessly," or "waste money on." Other synonyms might include "pay through the nose," which suggests paying an exorbitant amount, or "get taken advantage of," which implies that someone may be charging you more than what they should. Regardless of the specific wording you choose, the important thing is to convey the idea that paying more than you should is not a wise or desirable choice.