User blog comment:BorosPaladin/"Must Have" for Season 3/@comment-81.51.16.158-20121217101233/@comment-101.161.27.34-20121218012523

It's 700 (cost of Sight Stone) / 75 (Cost of a Sight Ward) = 9.33

The cost does not include the bonus health. Although:

1000 (cost of Giant Belt) / 400 (HP from Giant's belt) = 1HP for 2.5g

soooooo 2.5 * 150(Hp from sight stone) = 375.

700 - 375 = 225g is how much you're paying for the ward portion of the item effectively.