Okay, so my friend has recently enrolled in this $300 choir camp and is joining choir next year because he is convinced that this is the only way to improve his voice. Now, I don't object to him doing this, but I just think there would be easier ways to improve his voice. What do you guys think?
It'll help if he gets a good choir director.

I joined the Chorus at my school this year, which I presume is probably a similar organization, and it helped a lot.

It helped me learn how to sing in my own voice, which was a big problem for me, but I can only speak for myself.

The director taught also us how to manipulate our vocal chords so we could get different sounds out of our voices, almost like adjusting the tone knob on your guitar.

If he's spending that much and going to a camp, I bet you'll see an improvement in his voice. Any practice is good practice, especially if it's practice with someone who really knows what he or she is doing, and can tell you what you are doing incorrectly.

EDIT: Actually, not any practice is good practice, because if you sing the wrong way you can really hurt your voice over time; this is why it's good that he'll be working with a professional for a while. Sorry about that.
Peace, peace, and that's my piece.

Just another pale, skinny, noiserawkin' indie boy with tousled hair

Since I knew nothing about my voice, joining chorus helped give me direction under the supervision of someone who knew what they were talking about. But that's just me, and I got to take the course for free.

Try to see how much individual attention he'll get.... the more the better (obviously).
It all depends on how long/many sessions the camp is, how good the teacher/director is, and how small the group is. (smaller the better)

He could've looked into getting a voice teacher for, say.. 50/hour? (dunno how it is locally at your guyses places, but i know where i live its between 40-100 cdn, but a lot of them are 40/hour to attract the smaller budget people)