Sharia law solves the problem cleanly by requiring the man to agree on a fixed sum deposit (Mahr) in the divorce contract that the wife will get on divorce (with some paid up front and some potentially deferred to divorce time), rather than agreeing to an arbitrary large liability. For people who don't like that idea, consider that if current western divorce laws aren't reformed, and marriage and birth rates continue to dwindle, it'll eventually become the law of your land purely by demographics, as natural selection favors cultures that encourage higher birthrates.