We've been delinquent in posting Financial Updates, but here we go.
Uruguay: $110/day. Tough to call this a good average since we were only there for two days. In general, though, there isn't much to do in Uruguay. Food is more expensive than many South American countries, and you have to look around to find good deals on lodging, but there aren't a lot of tours or other expenses even if you were looking to spend money. A lot of hotels seemed to have raised prices dramatically, but we ended up finding a very nice room for less than $30/night in Montevideo.
Argentina: $115/day. Transport in Argentina is a good deal cheaper than Brazil, which helped to keep costs down. Lodging continued to average $20-30 per day. Food is a bit more expensive, but still cheaper than the US. We took a few different tours in Argentina, which were reasonable, but not super cheap.
Chile: $108/day. This one actually surprised us. It seemed more expensive while we were actually there, especially considering that we took the somewhat pricey boat for three days from southern Chile to slightly less southern Chile. Transport was much cheaper in Chile, though. And we didn't eat out much. Overall, a really good value.
Bolivia: $63/day. This is not including the cost of being robbed, which would have added close to $1000 (about $50/day) to the cost of the country. It does include the $270 for visas, though, so it would have only been about $45/day without the visas. It is by far the cheapest country in South America. Tours and lodging are both very cheap and transport is fairly cheap as well.
Peru: $87/day. Peru ranks high on the value scale. It is cheap, but you can normally find decent quality buses, hotels, and tours. We took some really nice buses for just a few dollars more than the poor local buses. Machu Picchu is expensive (and worth it), but the rest of the country is cheap.