Dipper has gone to a lot of haunted houses in his time, most of them for the sole purpose of breaking his jumpscare reflex, which he discovered to be kind of overactive in his time at the Mystery Shack.
This one's a bit different, though; the scares are pretty tame, of course, but as he makes it to the exit, he can't help the question.
"So, I've gotta ask," he says, as conversationally as if he was asking about one of the spring-loaded fake-spider launchers, "why are a bunch of actual, legitimate ghosts running a hokey, fake-looking haunted house?"