The cost of Phentermine varies depending on location. Typically, it is quite affordable, ranging in price from $10 to $20 for a common dosage of 30, 37.5 mg tablets. Island Medical & Beauty Clinic makes sure Phentermine costs are as affordable as possible. Pharmacy prices for generic medications are typically lower than those for brand medications, regardless of where they are sold. Common prescription medications come in generic forms, so you don't have to pay the higher brand name price. Ask your health care provider if generic Phentermine is appropriate for weight loss.