It used to be so simple when pricing airline tickets. A roundtrip ticket was usually less expensive than buying two one-way tickets, especially if you planned your trip to stay over a Saturday night. 

But those days are over, and these days, a roundtrip fare may not be the best deal.

Many different airlines, especially low cost carriers, offer reasonable one-way fares. But on international itineraries, the opposite is true. 

Roundtrip tickets are almost always less expensive than two one-ways.

With one caveat: if you’re not sure about your return flight date, then buy a one-way ticket, because many international carriers impose excessive change fees.