Honestly, if you know a publisher that only takes a 10% cut on a game's sales, you should tell companies about them, because I'm sure they'd all love to work with them. 10% is very, very reasonable.
5% for Amazon payments is pretty standard. Paypal's
fees are 2.9% + $0.30, which on a $15 transaction (the majority of the Kickstarter pledges) amounts to 4.9% — and they have extra charges for international payments.
And 5% for Kickstarter is also reasonable. They offer a platform, a reputation (you're not giving your credit card number to some seedy, unknown website), tools to manage your relationship with the backers[1], ways for people having backed other projects to discover new ones, and, since the success of DFA, a very recognizable "brand" for gamers. 5% for all that doesn't strike me as unreasonable, at least for a small-ish project (obviously, if you have a $200m budget, 5% of that for a webpage and some social tools might be a bit much).
[1] Jane Jensen says on her Kickstarter page:
"Why use Kickstarter? We needed help managing our CSG members. Can you imagine sending builds to 10,000+ different emails? Kickstarter manages all that for us, so we can easily run a campaign drive and post updates as often as we like."