We last visited Buenos Aires in 2010. When we flew into Eze airport we paid the $131 reciprocity fee charged to US Citizens. We are returning in two weeks, Feb, 2013. The new fee is $160 and they say you must pre purchase and present the receipt from your on-line purchase. I thought our 2010 entry fee was good for ten years. Do we need to pay again? If not, is the entry stamp from 210 in our passports sufficient evidence to gain us re-entry without paying again?