If I ask the client between shipping a bug now and then and developing twice as slow, I know what he'll tell me.

(edit: twice as slow is about the same as twice as expensive)

Shipping bugs is not a show stopper. It's not even serious. What is serious is developing a live, production app without any consideration for bugs: backups (at least a couple of very different kinds) and control keys. A control key can be anything which will be visibly not ok when there's a bug somewhere.