There's a market exchange rate (different from the official exchange rate), and if you could buy the pesos for less than that market rate, you could make money.

If you (a bitcoin seller) were to acquire pesos and hold them, it wouldn't work too well, as your money would get inflated away, eliminating and reversing any profit. However, you could instead (i) use them for transactions, or (ii) sell them to somebody else who has, say, dollars, but needs to buy assets in Argentina.