As a rule of thumb, the prices you can expect to pay in Argentina are double the American retail price.
Since nobody has imported Colts for a while (Gun Parts on Av. Independencia is alledgedly going to start importing them again) prices can get pretty steep for some of the older guns (even those that were police or army issue decades ago). I have nothing against old Colts, but you've got to be very knowledgeable to pick a good one (I'm not). Who knows what abuses, or so called gunsmiths, the poor gun has endured in the past fourty years?
I paid 1200 dollars for a brand new Colt 1991 a couple of months ago, I got it from Tirito (TIRITO.COM.AR) his service is fantastic. The only downside is that he deals in cash only, but his prices are fair and he is honest about the guns he sells.