We don’t really focus on price point as much as the “perfect item” that supports their interests. This can mean we spend anywhere from 20 dollars to a couple of hundred any given year. Of course, right now, my children are under 14 and not quite aware of the electronics world yet. There interests are more like rock polishing and wood-turning!
As an aside, If he is starting to do trips away from home an ipod touch can acutally become a useful communication and scheduling tool, not just entertainment. It also becomes the sort of gift that can grow with him, you can buy him accessories and itunes cards for future gift buying occasions. It is even something he can use while mowing lawns and to manage the business.
Since he is already working towards his trip and you are obviously concerned about him being balanced I don’t think you need to fear him getting out of whack. Besides, knowing how to relax and enjoy life is a needed skill. How about a gift certificate for a $150 to the online apple store? He can use it for the new ipod nano or save up for an ipod touch on his own? You can present it as “We see you maturing in responsiblity, we hope this helps.”