I go to the Swiss Medical office in Ramos Mejia (it is NOT a medical facility, just a business office), and tell them the cost has gotten so prohibitively expensive that I might have to find another prepay. I already have the lowest tier, so there is no other option to reduce the cost. The clerk commiserates (she's said my monthly cost is higher than her entire salary). How about a temporary discount? She smiles and says that she can do a 10% discount for 6 months. I've asked for this every 6 months for the past several years, never been told no. It is still too damn expensive, but it helps.
Many businesses will offer a discount to keep your business, but you have to ask. That info won't be volunteered. Every place I make a purchase, I ask "How much is that in cash (effectivo?)" and generally pay less. It never hurts to ask. This used to embarrass my Argentine wife... now she fixes a steely gaze and asks herself. I smile... and save a bit of money.