A few searches on Google gave me the statistically cheapest airports in each region. I used a few of the cheapest and gathered my information with a lot of trial and error searches. The dates April 13 through May 5 were choosen because they were dates that continuously showed lower rates among many travel sites. These days are in months that I would personally like to travel in. I love Spring and Fall weather, so these dates being appealing to me and my wallet lead me to pick them over others.
To travel to Europe for three weeks (April 13-May 4) the cost would be $619.89 through Delta.
To travel to Asia for three weeks (April 14-May 5) the cost would be $564 through American Airlines and a Chinese Vista would cost about $140.
To travel to Africa for three weeks (April 14-May 5) the cost would be $718 through both Lufthansa and Ryanair.
To travel to South America for three weeks (April 14-May 5) the cost would be $673.40 through United Airlines.