Reserving this spot, as I believe graffe, and you, are wrong. If I recall correctly it was 475 mana for 1600damage and changed later on.
Ok first, knowing graffe as I was a wizard in 1999-2004... He liked to post things from Spdat files in his daily news. In this link he posted the spell data from test, before kunark was released.
http://web.archive.org/web/200103041...ion_spells.htm
Sunstrike 1600 damage. No mana listed unfortunatally.
Here is a link from casters realm , please note what it says above the cast time.
http://web.archive.org/web/200105041...sp?SpellID=322
If you dont wanna click the link it says " On March 29 this spell had its mana cost changed from 475 to 450"