Adding Georgia
There are currently three different ways being recommended to add Georgia to your list of states where you can legally carry: Florida, Pennsylvania and Utah non-resident permits.
Here is the cost of each of those:
Florida: $117 and a bunch of paperwork.
Pennsylvania: $26.00 and very little paperwork.
Utah: $62.25 and taking a course taught by a Utah-certified instructor.
Source: Handgunlaw.us.
As you can see, using the Pennsylvania non-resident license is the most cost-effective way of adding Georgia.
Update: As Bill points out in the comments, New Hampshire ($100 for a 4 year permit) is also an option. This used to be the go-to permit for South Carolinians to add Georgia, until the New Hampshire governor raised the cost from $20 to $100. Adding New Hampshire, however, does add a few more states than the Pennsylvania permit and the paperwork is not complicated. The individual CWP holder will need to decide which option best fits his/her travel pattern.
Training for Life LLC's Official Weblog 
You left out the option of obtaining a New Hampshire non-resident permit. The fee is now $100 for 4yrs and a 1 page application, but the permit will also give South Carolina CWP holders the states of Alabama, Mississippi, Georgia, Pennsylvania and a few others. Turn around time is said to be swift also.