I don't know about the prices in Vietnam, the only info I know regarding this issue that in Paris is cheaper than my country Dubai. Also i heared from my freinds that prices in Hong Kong is very cheap.
as far as i'm concerned, the only thing worth buying in VN to be cheaper than most other places, are cheap (quality) clothes and authentic food. lol. $1 USD can buy a whole day's worth of food or maybe even more.. the average household income outside of westernized hanoi is about $30-40 USD.