We did this as well. My friend and I did drinking around the world.  I don't remember the cost because we both took turns buying.  We bought 2 beers (we only drank beer) on the first stop.  On the 2nd stop we only bought 1 drink and poured it into one of our cups.  We did this until the end of the night.  I do think we bought 2 drinks when we knew we were going to like the beer we were getting.  I was fine at the end of the night.  My friend was another story.