I have been saying that for a long time. Somewhere along the way Ted Williams and Charlie Lau and a host of other's somehow didn't know about hitting a Baseball. All of the terminology changed as if the old terminology was invalid. The real problem is that most people don't understand what the terminology actually means and just like to regurgitate it. I guarantee if Ted Williams was 20 today he would still be a great hitter. In my day the the buzz word was to "swing down". I could never get anyone to actually explain to me what that meant. They would just keep blurting it out. Seemed counter intuitive especially since Ted Williams stated that the bat path was on a slight inclined plane. Today you might know it as "hands inside the ball" or "knob to the ball". Some years back I listened to some hitting instruction breaking down every single movement and position during a swing. I asked him how can you swing a bat and NOT do some of the things he talked about? He didn't have an answer so I then asked why worry about those things?
The sad thing is that by turning your kids over to "experts" you are missing out. My father, my brother and I dug all that knowledge out of the dirt. We read and watched and talked to all sorts of information sources and providers. We would try things and used what worked for us and let go what didn't. We then went to the field for hours and hit and pitched and built great memories. We looked for the best competition we could find and tested ourselves. AND when we weren't doing that, we played stickball and wiffle ball and cork ball and hit ping pong balls in our basement with plunger handles. So please first of all enjoy your time with your son or daughter and be involved. Don't just be a chauffeur and an observer.
To answer the original question I agree about getting a used bat for 4 to 12 year olds. You will have plenty of time to buy expensive stuff later if your player continues. I don't know about today's bats, but I needed 2 or 3 bats during the course of a year when I was in High School and later. They would either dent, crack or just lose something when you hit that much. Even the Green Easton I always had 2.