CichlidFish.com - Fish That Think.

what would be an average amount for a pair of convicts?

cons are cheap! i wouldnt by a pair thought, i would just buy a male and a female. when stores sell cons as a pair, they usually cost more than 2 indivduals. 1 convict cost about (3 or 4 inches) cost about $3-4 . if you buy them young (like 1 inch) they cost about a $1 or less each.
male convicts: have longer dorsal fins and have a hump on their forehead.
female convicts: have an orange patch of scales on the sides near the belly. you can see it stand out usually.
you probably knew how to tell them apart, but just in case
so remember to just buy 2 indivduals.. theres a fish store i go to which sells a mating pair of convicts for 20 bucks! once you have a male and female, they are shure to breed.

if you get lucky, you can find a store with an over abundance of cons (since they are easy to breed, stores usually have quite a few). i found a store that had them for $0.99 a piece because they had gotten a large shipment of them in. good luck.