Per the profile, the OFFICIAL rules & cost:
-- offer ONLY to those booked in 'U' class or higher
-- one-cabin upgrade only
pricing for international travel, Y-C only:
up to 550 miles: $56
551-1050: $114
1051-1050: $171
2050: $229
2550: $286
3050: $344
3510: $401
4050: $459
4550: $416
... I didn't have time to copy any more, I'll update later : ).