BRK.A are "voting" shares. My understanding is that they want to keep the "voting pool" to be richer / upper class people.

Rumor is that the shareholders meeting is a giant party, a who's-who of the elite world. You can only have that culture if you have a very high barrier to entry. In any case, the high share price ensures a certain class of people in the voting pool: an old-school sense of community and elitism but... hey, you can't argue that it doesn't work.

Not much other reason needed.

Buffet has said before that it's intentionally high to keep out short-term traders and inexperienced traders. He wants investors who will hold for long terms. If the price is so high, there's only a particular clientele that can afford to buy it.

They do have a different code of class b stock that is more affordable.

I read it's because he only wants the most absolutely committed investors owning shares, not superficial speculators. You would overthink if you had to spend that much on a single share.

Although modern platforms with their fractional shares might negate the advantage a bit.

One reason is that they now have the highest stock price and that's a cool selling point for BK. Not their only one, clearly, but a neat point to make.