Where the money goes

I received a call yesterday from some "Cancer" related organization, I wish I remembered their name. In any case after getting this pitch to help those with cancer I was asked for a tax deductible donation with $75 as the suggested amount. I asked how much of my donation would actually go to the charity. The caller hemmed and hawed for a moment and then said she thought about 10% went to the charity. 10%? 10%? 10%? If the charity on whose behalf this call was made is a legitimate charity why would they allow this? I understand that it is essentially free money to the charity, but come on, only 10% of what's collected? This is part of the reason almost all my charitable donations go through my church.