Hey, B.S.! :)
Isn't there, in the DMG, some rule of thumb about enchantments that are available only to one class/alignment/whatever?
So, figure out the cost of a +2 sword. (8,000?)
Then figure out how much more a +5 holy sword costs than a +2 sword. (98,000 - 8,000? 90,000 net?)
Apply...