On the USA Today site they say: “A mailed-in return costs $2.49 to process vs. 78 cents for one that's e-filed, the IRS says.” Why do they charge $15.95 for an e-file then? I can mail my return in for a lot less than that.
I e-filed this year because I finally purchased a PC based tax prep software program and they offered a mail in refund for an e-file of my federal return. At that price I thought that was worth trying it out. It was nice but I certainly won’t do that again next year without the same offer.