In the case of Apple, anybody who is investing in stock, should be able to afford $500. I can understand the desire for tracking funds/BRK-B, when it comes to $150K+ shares on the part of an investor, who may not have $150K laying around to buy "a" share. In this scenario, there was a very real risk that third-parties would start buying up Berkshire Shares, and get voting privileges, while reselling the tracking stock. I think this is an issue for stocks once they get north of $10K (though, it's already an issue with other index tracking stocks - it just gets a little accelerated when the index consists of only one ticker)
At the very least, that's proof that the market wants shares that trade at less than 6 digits. It's not the same as "rational", but we do our best.