1:1 Computing costs are a difficult thing to nail down, because there are so many factors that go into it. I worked with GeSCI's Roxanna Bassi to create a worksheet to help guide cost calculations. I took a first stab four years ago, and came out with a $972/laptop cost over a 5 year program. To say that that cost estimate was not popular at the time would be an understatement.
OLE Nepal has put together a great TCO of the laptop program, based on their pilot project. Where I pieced together training budgets from USAID ICT4Edu projects and Internet connectivity estimates from UN/ITU global averages, they have on-the-ground numbers, (and a few ideal estimates on repair costs). The total for a 5 year program in Nepal? We're still looking at $753, if you read carefully: