The theaters don't make much off the first weekend's totals (that forces them to keep movies playing longer). The studios know that the majority of a movie's box office comes that first weekend, so they make sure they get the vast majority of the cut that week. A theater's cut gets bigger starting the 2nd week.
Van Helsing also most likely spent a ton promoting this film. VH didn't have any major tie-ins, like McDonald's (or MLB in Spider Man 2's case

), so their promotions budget was probably bigger. With this healthy opening, I don't think they'll have any trouble getting all their money back and turning a nice profit (especially on the DVD sales).
I haven't seen it yet, but I plan on it hopefully sometime this week. Next weekend, though, is "Troy." And I WILL be seeing that this weekend.