A random google search brought up these costs for FF games - although I've no idea where their source is:
In Dollars:
FFVII : 26 million
FFVIII : 30 million
FFIX : 38 million
FFX : 40 million
FFXI : 12 million
Those are total costs including marketing.
It's an old forum thread so FFXII wasn't out yet, although I'm sure I read it has the same as FFX roughly.
So I'd guess FFXIII is getting on to somewhere in line with $60-$70 million total costs, with marketing and such like. It has a higher retail price then previous FF's to justify the extra investment.
Where I got figures from: http://forum.beyond3d.com/archive/index.php/t-2832.html
It's amazing how much they spent on the PS1 games imo.