I couple of buddies of mine toured coast-to-coast of the US on $5. They still argue about who ordered the coffee. They went across twice, that time being the cheaper. They also toured from Alaska to Tierra del Fuego without funds, stopping and working when they had to. There is essentially no limit either up or down. It just depends on the person, their adaptability and self-promotional social talent. My wife and I spent about $1700 on our three week Czech tandem tour, counting art and other purchases, not counting the plane tickets, which were another ~$3,000 including tandem bike, etc. We camped some but took no stove, as eating locally and talking to the locals was part of the experience we were looking for.