It's 1.5 per 1%

I'm going to miss Rabadon's- I'd rather not have to waste gold on Armor when I bring Veigar in.

So just like TT, like I assumed. Thanks Nome.

are you sure you understand what happened there cuz witchcap is kind of better in every way

It has 40 less ability power and a 5% lower ability power bonus while only costing 100 less.

It isn't better in every way- though some will prefer it to Rabadon's.

Personally, I'd rather have more raw damage than some defense: armor is a trash stat on Veigar, and while he can use the active to some extent, he does not synergize well with it.

EDIT: I also view the Blackfire Torch as poorly focused for truly damage-oriented mages: requiring gold wasted on survivability stats with an active that does not scale with burst damage due to a DOT effect and no scaling on AP.

Its more of a tanky mage's item than one for a truly damage-oriented caster.