that Burger King commercial

This commercial, too, is fully subtitled despite the lack of foreigners. Obviously, I've seen this sort of subtitling before, so it's not new to me. I often wonder whether it's a thing that was picked up from the Chinese, who also subtitle everything (although, in the case of the Chinese, one reason for doing this is the profusion of dialects, thereby necessitating subtitles to help people understand the dialogue). Are there mutually incomprehensible dialects in Korea? I mean, I had trouble with the way people talked down in Daegu, but the language wasn't totally incomprehensible. Anyway, here's that Burger King ad:

I understand, pretty much, what's going on: the man comes into Burger King and wants a hamburger value meal, and when the cashier gets ready to tell him the price, he flatly declares the price to be "four dollars." The cashier lamely tries to tell him that his value meal represents a lot of food, but he keeps insisting that he'll only pay four dollars. The cashier finally relents and charges him W4,900, which is, as it happens, almost exactly four American dollars. The man breaks into English with an, "OK, thank you!" and formally, stiffly shakes the cashier's hand. I think the male actor does a hilarious job of deadpanning the whole way through, and the surreal situation that played out was also pretty funny.

Here's what I don't get, though, and I'll rely on Korean-fluent Charles to decipher this for me: when the man grates, "Four dollars," the screen flashes "사딸라" (sa ddalla) and not "사 달러" (sa dalleo), which is the usual Korean spelling for "four dollars." Is there some sort of pun that I'm missing? I feel there's another layer of comedy that I'm not getting at all.