I have played with a lot of soil compositions since I started this. NAPA 8822 and grit was my first mix, and it worked fine but you will likely put up with other people telling you its terrible. Many people in my club use a product called Mule Mix thats found at the co-op - its basically turface - their trees look great. I have used Bonsai Jack soil and it has also worked fine, I have had trees in it for almost 3 years and they're very healthy. I have also grown out trees in Brent's mix (from Evergreengardenworks.com) of large fir bark, large perlite, and peat moss - it worked out great. I also have two mixes I made of either large DE or Expanded clay, pumice, and lava and trees seem happy in it.
Basically, it seems like as long as you observe good watering and fertilizing practices for your trees, they seem to be happy in a variety of substrates.
More importantly for me is the factor of time and effort versus money. $50 for a bag of soil seems a high price until you look at how much time you spend sifting and mixing $30 worth of components. What is your time worth? I decided I like the process of mixing up soil so the time sink is worth it to me, I throw on some music or a good podcast and get to work. However, if you're getting $20-$30 an hour at your day job, why spend the time mixing and sifting when it comes out to just saving yourself $15 from buying a good soil premade?