Here are some of the bus fares I paid in 2012 and 2013:
Huay Xai – Luang Namtha (local bus): 60.000 Kip
Luang Namtha – Pakmong (Nong Khiaw) (minibus): 120.000 Kip
Luang Prabang – Vang Vieng (VIP bus): 150.000 Kip
Vang Vieng – Vientiane (VIP bus): 65.000 Kip
Thakhek – Pakse (VIP bus with Lao A/C): 70.000 Kip
Pakse – Champasak (minibus): 55.000 Kip
Champasak – Don Det (bus): 70.000 Kip
Don Det – Pakse (bus): 70.000 Kip