Hello @trangpu, where is Con Dao? in what country? Tkanks to #thediarygame I am knowing the world without traveling..!
Certainli, as you say, the cost of things in a island are most expensive that on inland, that happened to me before.
I would like to get an idea about the relation between the price of the train ticket and the distance of the trip; how many Kilometres is the train trip to Con Dao from where you were? I think, 30 or 40$ is very expensive.