Paris has a zonal system though that goes up past €10, which NYC doesn't do. I'm not saying that 'central zone' fares aren't ~$3 in many cities, it's very odd to only have one zone and the fare be that low.

Keep in mind the distances that the subway does (and has express service on) make it similar to the RER in Paris more than the metro.

It's been a while since I took the Metro but I had been all over on it including to "end of the line" stops outside the boundaries of Paris and it was always the same price, EUR 1.40 (back then).

You might be thinking of the RER, that has different pricing.

I understand your point now though: it's the long fares that are insanely cheap, due to the flat pricing model. There are only a few comparison points I guess since very few cities have a "subway" system that large (some may have large transit systems that reach the suburbs, but they are often separate from the subway and with a different pricing structure).