Currently 24 pesos for the sandwich the Stacker is really all I'd ever get at BK. It used to be around only part of the year but recently they very wisely put it on their full-time menu to avoid more aggravated homicides by hungover patrons craving a stacker. Per the norm down here the meat is better than most fast food burgers and with the triple there is plenty of it. Otherwise a simple burger, lots of cheese and bacon (a rarity) on top.
No sign of they mythical BK long bun burger in South America