Didn't he have several high paying roles in his career?
He should have invested his money...
He did, but during his best earning years, he did odd things like giving $1.5-2 million dollars to the IRA, which killed his box office in England for many years. Another big one was trying to buy and hold a mega mansion in Beverly Hills (He loves living like old Hollywood), which at one point had him taking any role to keep afloat. Harley Davidson and The Marlboro Man is a famous one from this time, he hates that film, but it bought him a little more time in that house.
He also turned down the role of Butch in Pulp Fiction a year or so later.
Now, he supposedly doesn't get paid much for Hollywood work, but does it at a lower price to bump up his pay on those B and direct to video films. For instance, he only reportedly got paid $400,000 for IronMan 2, and was only offered $250,000. He's also a loose cannnon on the films, for instance, he shitted on IronMan a bit after it came out.