I come into Ezeiza every month. I can tell you that they have a new boss at Ezeiza the last fast months and that the customs officials are checking everyone, including tourists, much more closely than in the past. Part of a general "clean up" on alleged abuses, bribery scandals, and lax enforcement of tax laws. If you have things that look new (especially electronics, etc) and you don't have receipts, they can and will enforce the duty limitations. I had two friends go through Ezeiza in the last couple of days and they had to pay duty. But the main thing they are looking for even with tourists is quantity. Quantity indicates gift or resale....just common sense; and those are definitely subject to tax. If you are not a local and speak very good and almost excellent castellano porteno, I would not recommend offering bribes or slipping bills.