Yes, the cost of limes does fluctuate, which can be frustrating. Pick a verdulería and stick with it, make friends, and you'll be less likely to get screwed. I get them at the indoor market in San Telmo, since that place has exotic and tropical stuff all year long, which means I can always go to the same person no matter what I cook. Tropical stuff is always expensive (10 pesos for a not huge mango!), but at least it's there. But even so, I can make a huge, party-sized batch of guacamole and pico de gallo for around 60 pesos total, tastier and cheaper than in any of the restaurants, so I don't feel that bad about it. (Two years ago the same recipe cost 45 in the middle of winter, oh well). But then again, that's only like 4 limes. Guess I won't be making key lime pie or ceviche anytime soon.