The Vienna, Va.-based Navy Federal Credit Union, for example, has a heavy concentration of military members who are constantly deployed or stationed overseas. In January, the credit union, which has 2.4 million cardholders according to Vice President of Credit Cards Randy Hopper, eliminated the last of its foreign transaction fees across the board.

Hopper said the $73 billion credit union, which has six million members, started eliminating foreign exchange fees on two of its cards about three years ago.

"That benefit was something that we knew they would value," Hopper said.

Member characteristics were also a big factor for the Alexandria, Va.-based Pentagon Federal Credit Union, which has $19.5 billion in assets and 1.4 million members. It too does not charge foreign transaction fees, according to spokesperson T.V. Johnson.

"We were actually one of the first credit unions to waive these fees, and the decision came out of providing the best value to our core membership which includes military personnel, defense contractors and their families," he said.

2. Marketing prowess. To maximize the return on switching to low or no foreign transaction fees, credit unions have to find ways to make members more aware of their cards' new value proposition. For example, Navy Federal tied its fee waiver announcement to its rollout of EMV cards.

Credit unions thinking about eliminating foreign transaction fees should remember that the change also means updating their websites, orchestrating and sending email blasts, writing newsletter copy, reprinting brochures and other collateral, as well as talking to or retraining the branch staff.

"You have to make sure that you have it as a message across all channels," Hopper cautioned. "So if they call in, if they visit a branch, if they go online, you want to make sure that the message is consistent."

3. A business case. Ultimately, the decision has to make financial sense.

"We did see feedback from members in the form of higher account openings," Hopper said. "We saw higher compound annual growth rates in both of those products above and beyond what we have been seeing from a growth perspective."

Ray Crouse, president/CEO of the Pasadena, Calif.-based Parsons Federal Credit Union, is understandably skeptical about how those results would apply to smaller credit unions like his. Parsons, which has $222 million in revenue and about 6,600 members, caters to engineering firms with employees all over the globe who do a lot of traveling.

Parsons's credit cards carry a 1% foreign transaction fee – well below what the CreditCards.com survey found was an industry average of 3%. It makes just about $6,000 a year on foreign transaction fees, Crouse said, and those fees cover fraud risk, additional support for members overseas and work necessary to help faraway members with lost or inoperative cards.

"If we tripled it, it'd be $18,000 a year," he said. "For a small credit union, with the interest margins the way they are, every little bit counts. Now, I would love to have an extra $1,000 a month if we just took it to 2%, but that's just not our business strategy. It's a give-back to the members, and we do realize they recognize it."

Hopper is familiar with that urge to tread carefully when it comes to turning off fees. Navy Federal took several months to make its decision, because it's one it will likely have to live with for a long time.

"Once we eliminate a fee, it's gone," he said.