Avacados happen to be one of the more expensive vegetables.. and the price is highly seasonal. You should see them for $0.8 to $1.2 "in season" and $1.5 to $2.5 "out of season". Perhaps an additional tax if you live in a big city.
if you want to talk about vegetable affordability, lets start with lettuce, carrots, and broccoli.
Most stores I've seen in Manhattan have them between $2.50 - $3.00 lately. However the fruit vendors on the street have them at $1.50. Usually 2 for $3.00.
But you probably want to use them that day which I see as a feature.