People who don't shop around pharmacies for the cheapest prescription drugs could be overpaying by as much as $100 a month, according to an article by Consumer Reports.

The publication gathered its information through undercover journalists who pretended to be uninsured shoppers as they called over 200 pharmacies throughout the country asking for the retail price of five of the most demanded drugs: the diabetes drug Acots, the antidepressant Lexapro, the cholesterol drug Lipitor, the blood thinner Plavix and the asthma drug Singulair.

What the callers found was as much as a $749 difference betweeen the highest and lowest priced stores. For example, one month's supply of generic Lipitor costs $17 at Costco whereas CVS sells it for $150. Rite Aid and Target both had prices similar to CVS.

One possible reason for this that the article explores is the variance in business models among the different companies.

"It really comes down to a store's business model," Consumer Reports Editor Lisa Gill told Reuters. "For example, big box stores tend to use their pharmacies as a way to get consumers through the door with the expectation that they'll buy other things."

Senior vice president of pharmacy for Costco Victor Curtis refutes the idea, however, that this is the model his company is working under, stating that the pharmacy itself is profitable.

One of the most important messages in the report, according to Reuters, is that customers only need to speak up as pharmacists will frequently help the customers save as much money as they can.

"Especially for the independent pharmacies, if they want to retain your business and loyalty, they will help you get the best price," Gill said.

Finally, Consumer Reports recommends gettnig refills for 90 days as many companies will offer a discount for 3 month supplies.