A 2005 study of households with incomes from $200,000 to $500,000 per year shows average charitable giving of $40,746 per year.
John McCain has given $202,000 to charity in the last two years, about 25% of his income--but of course he is married to a very wealthy woman who earned more than $6 million in 2006. Last year he gave $105,467 (half of what he and his wife donated as a couple) on income of $405,409, which would be more impressive if it weren't just an even division of their reported expenses reported without the comparison figure of her income.
The Obamas gave $240,000 to charity last year on income of more than $4.2 million (5.7%). In 2000, they gave $2,350 to charity on income of $240,726 (1%).
Palin's tax data hasn't yet been released. There may be some tax problems lurking in her records.
John McCain's personal charitable giving appears quite generous, but it's somewhat less so considering his wife's much higher separate income and my suspicion that she effectively subsidized his charitable giving as the chief breadwinner and provider. The Obamas were very generous last year, but not so much in 2000. The Bidens, not at all generous. This seems to lend further support to the thesis that conservatives are more generous with their own money than liberals.
My feeling is that most professionals earning six-figure incomes should be able to give 5-10% of their gross income to charitable causes without much trouble. The average figures for those earning $200,000 to $500,000 strike me as just about right.