Hi,
I thru-hiked the AT in 2006. My total cost was about $6,000 including airfares. That did not include gear puchases as I already had plenty of equipment & was already lightweight, so i did not need/want to replace any gear as many people end up doing. There are a few things that will vary your costs.
1. How long you take to hike it. Obviously the faster you go the cheaper it is. I finished the trail in just over 4 months, which is slightly shorter than average, so my costs would have been lower.
2. How many 'zero' days you have. Rest days in town cost a lot more than days hiking as you pay for hotels/hostels etc. and restaraunt food etc. I had 5 zero days on my hike which again is lower than average & would have reduced my costs.
3. Your tastes & financial situation - While I do not have expensive tastes, I was working full time when I hiked & had saved plenty of money for my trip, so I did not need to really budget. many people on the trail are just out of college or retired & so have to be careful with what they spend. So this would have pushed up my costs compared to the average.
So as usual the answer is....it depends !...... but it is certainly doable in fairly comfortable 'average' manner if you have about $5-6,000.
There are a many websites with information about the AT, but one of the most useful ones for cost information is
www.whiteblaze.netIt is an amazing experience & I would encourage anyone to do it if you have the opportunity. let me know if you have any questions about the trail...happy to help out !
Cheers,
Chris