the total number won't affect whether you match at a "top choice." if your top choice ranks you to match, or makes their way down to you, then the total number you have to do is 1. for programs you're less interested in you have to ask yourself, "am i so confidant that i'll match somewhere else that i'll take my chances and save my money by skipping this places?" if yes, cancel away and hope that you're right.
i sorta think of this in poker terms. by this point i'm "pot committed" to the Match, so to spend more money to ensure i don't have to scrample, it's worth the money to keep playing. if you're a hold 'em person this makes sense, if not then just make the best decision you can. you're better off seeking advice from a dean at your school or someone in ob-gyn who can evaluate your total application rather than any opinions you'll get here based on incomplete information.