first, yes, it's cheaper, and yes, the wine i buy is better 100 fold than the states, and yes, i would say i've cut costs by about 40%. my kids didn't belong to a private club and take swimming and tennis lessons in seattle... so we're not taking advantage of the cost savings we could.
but it's still hard: hiring is hard. getting a good cultural fit is hard. building a business that works within the legal framework is impossible. i'm deathly afraid of hiring local talent because it's VERY easy to be sued due to the employment laws of the country.
but it's great: you get a lot of time back in ways i can't explain. it's like you get to ignore a lot of the BS that working in seattle or SF can overwhelm you. explaining the details of why that is would be a longer post, but every tech expat i know in argentina talks about the same thing - somehow you feel more in control of your schedule and your life.
do it when you can hire foreigners, keep your team small, keep your relationships and contacts with people back in the states or europe, and get paid in dollars or euros (or build a product that makes dollars or euros), and can come back once in a while - anything else and it's not such a great deal.