Well it's pretty expensive to fly to Argentina these days and it's not as easy as it once was to get cheap tickets. I would say you are looking at $1,000 unless you really do your homework.
Remember it is usually cheaper to fly from Houston than Dallas.
Obviously not traveling on the holidays is cheaper and sometimes changing the day of travel can change the price significantly, in my experience Tuesday and Wednesday seem to be cheaper.
Felicity- Hotel booking in Buenos Aires
Mexico Hotels