Remember that the platforms you use to crowdfund have fees associated with collection and access to the marketing tools they offer.  Kickstarter takes 5% of the money raised and Indiegogo takes 9% (but if you reach your goal by a specified time, they will rebate 5%). On top, there are 3rd party fees such as Amazon payments fee or Paypal fees to receive the money you raised. Then, there are your fulfillment costs associated with the perks you offered (DVD copies, tshirts, etc. & postage for these). Take these into consideration when you are figuring out how much you need to raise so you don’t run short.