Peach, not trying to be a dick, but your kid is wrong. The MLB HR record would be way over 100 today with aluminum bats & there would be 3-4 guys a year hitting over 400.
A $300 bat will hit a baseball on average ~5-10% further/harder than a $20 Walmart bat. I don't disagree with your statement, but for my son it did not matter a bit. I purchased a very expensive hard maple bat for him to use at a professional show case. He broke it on the first swing and had to pick up a junk wooden bat to finish his session. He continued to hit ball after ball out of the park. With that being said, one of his college team mates came out of high school as one of the nations all time best high school hitters. He continued that success through college and everyone thought he was going to make a great pro player. When he had to start using wooden bats in the minor leagues, he could not hit a ball deeper than the warning track. Hince, he only lasted one year because of the bat. So yes a bat can matter to some hitters but you are not allowed to use aluminum as a pro. A guy I coached and played with is in the high school coaches hall of fame and even though retired, he still is a very reputable hitting instructor. He will tell you straight up that hitters are born and I totally agree. When parents call him and ask for hitting instructions, the first thing he asks them is - Can your son hit? If they say no -- he replies: Sorry, I cant help him!