It's different in one very important respect; most likely, you are completely willing to admit that you like big tits. As you said, your ex girlfriend would never admit she wanted a man for his bank account.

The lack of honesty is why most people don't like golddiggers.

A golddigger [1] is morally equivalent to a guy who lies to women about wanting a relationship, simply with the goal of getting into her pants. Actually she is worse, since her actions are considerably more harmful.

[1] I exclude the honest golddiggers, of which I'm sure there are a few. I've got nothing against a girl honestly trading sex for money.