The agency has crunched the data and named the top 10 best value far-flung destinations for winter sun, based on the everyday costs of things like a bottle of water, suncream and cocktails.
In Hoi An, a three-course evening meal for two, including a bottle of house wine, cost from £40 (US$54) while a local lager costs £1.23.
Beyond the bargains, Hoi An is one of Vietnam's most photogenic cities, with cobbled streets curling around a lantern-lit river, world-class street food, idyllic beaches and a buzzing night market, it said.
Cape Town in Souyth Africa ranked second, followed by Indonesia's Bali.
The best value long-haul destinations for winter travel:
1. Hoi An, Vietnam
2. Cape Town, South Africa
3. Bali, Indonesia
4. Mombasa, Kenya
5. Tokyo, Japan
6. Columbo, Sri Lanka
7. Penang, Malysia
8. Delhi, India
9. Phuket, Thailand
10. Santiago, Chile