I do agree with Krokodil; the bus service in the whole country of Andorra is ok, i would say better than ok.Â
The prices vary depending on the distance, there are at least two bus fares: 1.50 euros from Andorra la Vella to Escaldes and Encamp (one way); and 2.90 euros to Canillo, El Tarter, Incles, Soldeu and Pas de la Casa (one way also).
I am not sure about the fares to other parts of the country like towards San Julia and other points in the South; and towards La Massana, Erts, Arinsal, plus Ordino, La Cortinada, Arcalis and other points in the Northwest.
I do like to ride them. They run about every 30 minutes (max) and save me good money in parkings, fuel and tolls. Most of the times i go or come to Andorra, i do not bring a car with me.
Adeu (good bye).
Txabi