It cost me about $1400 to hike from Happers Ferry, WV to Glencliff, NH, less the 100 miles of Vermont I skipped (Manchester center to Hanover), or about 700 miles. So, that works out to $2 a mile for one of the more expensive sections of trail.
I put $920 on my debit card and somehow blew through $500 or $600 in cash. (I forget exactly how much cash I brought with me)
$350 was spent on accommodations, $255 on new gear (boots, superfeet and a new shirt), the rest went to food and I was still hungry.