BALTIMORE -- A trip to the drug store could easily empty your wallet, so imagine how angry you'd be if you found you were paying too much. Not just a few dollars, but hundreds for just one drug.

Each year in the United States, almost 4 billion prescriptions are filled. Pharmaceutical sales is big business and most of us have to dig deep to pay for the drugs we need, reported WBAL-TV in Baltimore.

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For "Steven," it's a drug called fluoxetine -- the generic form of Prozac. He didn't want his face on camera, but did want people to know the discovery he made when he went to a Philadelphia-area Costco to buy it.

"They were charging me almost $300.00 at Rite Aid and it's only $17.00 here," he said. "There has to be a mistake."

But there was no mistake.

"This is the prescription I received at Costco for $17.29," he said. "The same prescription at Rite Aid for same amount of milligrams and quantity was $293.93."

A difference of more than $276.

"Steven" couldn't believe there was that big a difference in price and neither could we, so WBAL-TV started checking prices in the area.

For the same quantity and strength of fluoxetine, Costco charges $17.29, Sam's Club -- $49.62, Neighbor Care -- $176.09, CVS -- $184.89, Rite Aid -- $195.99, and Giant even higher at $258.14.

The TV station called Giant and asked: Why so high? They received a statement saying, "Our pharmacy operations conducts weekly price checks to determine if our pharmacy products are priced competitively. With over 3,000 items in our pharmacy inventory, occasionally a product is overlooked during price checks. Apparently that occurred in this case. Effective immediately, we will retail this product for $89.91."

"That really tells the consumer you need to ask about this to make sure you get the drugs at most reasonable prices," said Frank Palumbo, director of the Center on Drugs and Public Policy at the University of Maryland School of Pharmacy. "The pharmacies do charge differently depending on their needs what they pay for the drugs, their location, their expenses and a lot of other factors."

So the key is shop around. WBAL-TV checked prices on three other commonly prescribed brand name drugs.

For Lipitor, a cholesterol-lowering drug, the high price was Neighbor Care at $239.06 and the low was Costco at $182.07 -- a difference of $56.99.

Maxzide, a drug prescribed for high blood pressure, was $61.99 at Rite Aid and $25.07 at Costco for a difference of $36.92.

Vioxx, an arthritis medication, was $105.99 at CVS versus $77.37 at Costco -- a difference of $26.52.

If you have a prescription plan, Palumbo says most likely the insurance company has already negotiated prices based on volume and that helps. Still, AARP says many people are left out, especially senior citizens on fixed incomes.

"Most people over the age 65 that are Medicare beneficiaries only about a third have a supplemental insurance," said Donna Delano from AARP of Maryland.

Robinson said many people have taken to the Internet, buying their drugs from European countries and Canada -- places with government price controls.

"AARP feels its a national disgrace that in our own country full of medical technology and advances in this day and age that we have to go to a foreign country to get drugs that our residents need," Delano said. "We're very embarrassed by this."

While Congress wrangles over how to help people afford prescription drugs, some of those who can't may be cutting corners -- skipping pills and letting prescriptions go unfilled -- ultimately risking their health.