Hi Mark,
I was thinking that maybe on your site you could have an average cost per day table for each country in South America which shows what you should expect to budget for each day.
The table would be for travellers to estimate an average daily living rate in a basic but liveable hostel but exclude excursions, heavy drinking sessions, and anything that warrants paying a higher fee for a bit of luxury.
I think travellers should be able to see the following information in the table for each country:
Average cost per day in a shared dorm room in a hostel with breakfast included.
Average cost per day for a meal
Average cost for a beer or wine (everyone needs to know this)
Average cost of a taxi or bus from the main airport within the set country to it's main city centre
It would only be a rough idea of costs as you couldn't predict the exchange rate and price inflation, but it would still be a great way to help work out budgets and discover which countries are more expensive than others so you know which ones could eat into your budget.
I see alot of forum posts on several travelling websites which always ask how much for x,y,z so having a handy table to refer to would be a bit of a comfort guide for noob travellers.
Andy