Do you guys actually read the comics or just guess? If you read the comics, Bruce Wayne is far and away more wealthy than Lex Luthor... however, as Batman, relies on that wealth far less than Luthor relies on his wealth as a villain.
How do we know that Wayne is wealthier? Well first, let's put Luthor in perspective... he basically built modern Metropolis, after NML he literally moved and rebuilt Gotham on his own dime, the funded a bid for the presidency from his own pocket and won... that is a sick amount of money beyond anything in this world or the Marvel Universe.
Then why is Bruce Wayne richer? For starters, he's kept up with Lex every step of the way, in technology, struggling for control of new Gotham, etc. But most importantly, when Lex became the President of the United State, he gave up his holdings, his company, everything, so that there would not be a conflict of interest between his extensive corporate holdings and his duties as POTUS. What happened next? Wayne acquired it all. Bruce Wayne currently owns all his holdings and all of Lex's... he's richer than god... which only goes further towards making his character unrealistic, but those are the facts.