In the California Bay Area, We don't have avocados in a box, nor perfectly ripe. They are usually in a pile and quite un-ripe (which helps reduce denting in the pile). Depending on size, quality, and organic status they range from about ~1 to ~2.50 each.

You can also buy a full flat of medium size avocados at a Costco Business center for $26 for 35 avocados. They are "stage 2" ripened, which means they will be usable in about 1-2 days on the counter. I buy one and then put them carefully in the fridge and take out about 3-4 at a time. This way I can have fresh ripe avocados for about a month.