I would have thought that it should be the same as it is for answers. A good question is just as important as a good answer.
Question upvotes used to award 10 points. That was changed last year. From this blog post:
question upvotes will now grant only +5 rep instead of +10.* There is no change to answer upvotes. This will apply retroactively to all >users.
- While we value good questions (and asking a great question is absolutely an art), we want to explicitly encourage people to provide the best possible answers. Without people interested in providing good answers, the questions are moot. We know that answers have more intrinsic value than questions, and the reputation balance should reflect that.
- The question asker already enjoys a substantial benefit beyond reputation gain from upvotes on their question — namely, they get great answers to their question! Thus, the asker shouldn’t need as much reputation gain.
- There are a few users who ask hundreds, sometimes even thousands of questions. Over time, these users generate a fairly sizable reputation entirely through the tiny trickle of upvotes gained by these questions. In a sense, we want to discourage question asking a little bit, and make sure that people who ask questions are doing it for the right reasons and not to generate reputation.
See also this discussion post on Meta.SO.