Let's assume for the moment that permitting campaigns to be financed largely by donations from wealthy people leads to an agitated political economy, and that public financing of elections would alleviate much of that agitation.
How much would public financing cost?
Let's start with the amount of money raised by candidates for all federal elections in 2002 and 2004.
In 2002, Senate candidates raised $369.9 million, and House candidates raised $637.8 million. In 2004, the numbers were $542.7 million for the Senate, and $696.4 million for the House. Congressional races in 2002 and 2004 raised a total of $2.25 billion (source OpenSecrets.org).
In 2004, presidential candidates raised $880.5 million (source OpenSecrets.org).
Total receipts for 2002 and 2004 were, therefore, $3.13 billion.
This sounds like a lot of money, but consider that, in 2003, 88.9 million taxable returns were filed. Of these, 39.7 million were filed as "married, filing jointly", raising the total number of taxpayers represented by these returns to 128.7 million (source IRS). Divided among all taxpayers, the money raised in the 2002 and 2004 elections comes to $24.31 per taxpayer.
When split over the four years covered by the 2002 and 2004 elections, the cost of public financing would be on the order of $6.08 per person.
Now, consider that Medicare Part D will probably cost American taxpayers $200 billion. This comes out to $1555 per taxpayer over 10 years, or $156 per year over 10 years.
Which would you rather pay? $156 per year to have your elected officials make stupid decisions, or $6 per year to have them screw on their thinking caps?