[anotherthrow]

>Either they believe in paying a bigger share or they don't.

First, They believe in rules to enforce everyone paying a bigger share, and are lobbying to bring that about. There's nothing inconsistent in doing that whilst not individually making a bigger voluntary contribution. One might think that one's efforts are far better spent lobbying for a general rule then individually donating.

Second, people like Buffett have commitments to philantropy that I think would easily count as making a bigger contribution.