Kickstarter takes 5%, so that piece is likely negotiable. The 3-5% is for payment processing and it seems like it is through Stripe or Braintree. Both start at 2.9% plus $0.30 per transaction but bulk pricing is available at $80,000/month (which Kickstarter definitely meets). So there is some wiggle room on both side, but this is Kickstarters profits so likely won't cut a ton of percentage points.