We were thrilled when we found $730 plane tickets from Chicago to Vietnam.

Friends had recently traveled to Hanoi and Ho Chi Minh City, so we knew we’d need to get our visas ahead of time.

What we didn’t know was that we had booked our October flights shortly after the country changed its visa regulations.

In April, according to a State Department official, the U.S. and Vietnam ratified an agreement that permitted Vietnam to issue 12-month, multiple-entry visas to U.S. citizens. The U.S. similarly allows Vietnamese citizens multiple-entry, 12-month visas for short-term business or tourism.

But once the new visa regulations went into effect, we found that 12-month visas were the only ones available, instead of the former 30-day visa option. And the fee had skyrocketed.

Just how expensive was it? It depended on whom we asked. The Vietnam Embassy’s website (www.vietnamembassy.us) doesn’t list prices. It simply directs people to an email address and a phone number with multiple extensions. Phone calls to each extension went unanswered.

An email to vnconsular(at)vietnamembassy.us did garner a response within a day. The Washington, D.C., embassy cited a $220 fee. The Houston consulate, however, quoted us $200, and San Francisco, $185. (We reached out to Houston via 713-850-1233 and heard back from San Francisco after emailing info(at)vietnamconsulate-sf.org. We didn’t try the New York consulate, which appears to be reachable via info(at)vietnamconsulate-ny.org.)

Prices have since shifted; a recent email to the consulate in San Francisco offered an $80 visa for a one-month, single-entry visit, which would have sufficed for our vacation.

Because fees appear to be flexible, it’s a good idea to check with multiple consulates and the embassy for the lowest price. You’ll need to mail your passport and include a prepaid return envelope. Passports must be valid for at least six months beyond your planned stay.

Beware of scams. The Vietnamese government allows some businesses and travel agencies to arrange for preapproval for a “visa on arrival” at the airport, but the State Department warns that some U.S. citizens have reported being charged unexpectedly high fees upon landing in Vietnam. It recommends that travelers get a visa directly from an embassy or consulate of Vietnam before arrival.