$60 would seem steep to me as well, but it beats the heck out of the comparable cost of boarding your cat. And yes, you would spend about the same for the automatic feeder as you would for a kid to help out... but
If you get the feeder, is your cat going to be freaked out by it? Does it make noise(s)? Is it going to fit in the same spot as her bowl? What about water? Can you be sure she'll have enough water while you are gone?
If you have a friend (and their kid) help you out, they can make sure the litter is freshened up, the water bowl is full, that your cat is eating, and maybe even visit long enough for scritches behind her ears. If this is an adult friend, then there's a good chance that they would do it out of freindship. If so, @Berend's idea of a small thank you gift would be appropriate. If your friend's kid does it, then pay them based on their age. $5/day for a grade schooler, $15/day for a high schooler.