It will not cost SONY $1.5 billion....
Also the firm reporting this originally said $318 per account. Now its $20 per account. The figures are $x for security updates, $x for employee overtime (two weeks worth akin to the lead up to a console launch), $x opportunity cost for lost revenue while PSN is down, $x opportunity cost for PSN over ~2 years (PSN revenue will be down over what it would of been without the breach).
All in all i would estimate SONY will spend about ~$50 million on this, maybe another ~$5 million on the lawsuits they will win (your phone number, address, name, PSN username, PSN password don't need to be encrypted. PSN details are SONY's businsses and ph numbers, names and addresses are public information freely avalible little things called phone books). In addition to this they will have about $500 million revenue in opportunity cost, maybe $1 billion if news outlets keep reporting the worst case senario. This means that SONY will have up to $1 billion revenue less then what they would of had. This is likely to occur over about two years imo - after which time most of the general public will have forgotten about this.
