Antonyms for the phrase "easy on the pocketbook" could include words such as expensive, costly, high-priced, overpriced, premium, exorbitant, and inflated. These words refer to something that requires a significant investment of money or resources, and is not affordable or accessible to everyone. An antonym for "easy on the pocketbook" could also be described as a luxury or indulgence, where the cost is high and the benefits or value may not be worth the price. In contrast, "easy on the pocketbook" implies affordability, reasonability, and value for money, making it a desirable trait for many products or services.