Well that's awfully assumptuous. So now a young college kid needs to spend time and money to be able to help out a project? I also don't like that this model inentivizes a few big PR's over small, lean, readable ones.
We're completely mixing up the incentives here anyway. We need better moderation and a cost to the account, not to each ccontribution. SomethingAwful had a great system for this 20 years ago; make it cost $10-30 to be an external contributor and report people who make slop/consistently bad PR's. They get reviewed and lose their contributor status, or even their entire account.
Sure, you can whip up another account, but you can't whip the reputation back up. That's how you make sure seasoned accounts are trustworthy and keep accounts honest.