It depends on the page, and on the queries.
If you have a ridiculous amount of queries (like 40+) you probably have them executing inside a loop which is in most cases unnecessary. 1 poor query could have far more server load than 100 efficient queries could ever have.
But with only 13, you have nothing to worry about.
BTW, every vbulletin page will start with 5 or 6, not including the content for that page. If the page has a lot of different content coming from different places (not all from a single table) then it may take many queries to pull the data correctly.