Like Cambodia, Vietnam has developed at light speed over the past two decades. While prices have risen significantly since the late '90s and early '00s, when $10 to $20 per day was a reasonable budget, it is still possible to travel quite cheaply in this Southeast Asian nation. This is one of the few places that actually has a favorable exchange rate with the U.S. dollar.
You can get a nice meal for $5, though there are plenty of $2 to $3 street-food options on every corner in major cities like Ho Chi Minh City and Hanoi, while 50-cent coffees and $1 beers are the norm. Very basic $10 single rooms can be found in every city and town, and many locally owned guesthouses offer scruffy-but-livable $5 dorm beds as well. Low-cost airlines have come into the Vietnamese market, though the $50 to $100 fares are not as cheap as braving the famous Highway 1 in a bus or trundling along the scenic coastline in an aged train.