Andy Thailand: The Lao PDR VOA price can vary from country to country. It is US$10 cheaper to travel on an Australian passort (for example) than a UK one!
CraigWatson: See if you are able to get a VietNam based agent to arrange a VOA for you. We visited in April and it was a lot easier (and cheaper, even bearing in mind his $15 pp fee) for him to do the paperwork, which took less than a week. Just rock up with the documents and a photo.
You will end up with two pages of your passport transformed into works of art!