alternatives to FP cost for Requires Attribute Roll fails?

[Plane]

I was thinking about when you apply Requires Attribute Roll to a cheapy ability to reflect how it's sort of skill-based.

Like say for example you want to do High Manual Dexterity [5] reduced to [4] via Requires IQ Roll (-10%) and Limited Use 10x/day (-10%)

What you're getting any time you pass your IQ roll is a +2 to DX for fine tasks for a minute.

If you have a limited amount of FP, spending 1 FP would be a huge expense that would dissuade using it.

Obviously though being unable to use it due to a failed attribute check (especially if it has a long activaiton time, some things with Takes Extra Tiem do) is still a limitation even if it might be worth less than the usual -10% for not having a FP cost on retries.

Removing the FP cost has no clear guideline though since obviously a +20% for Reduced Cost wouldn't make sense (it's more expensive than IQ check entirely)

I don't know if there's a precedent but the best I can think of is reversing the enhancement into a limitation (-20%) which applies to the value of the IQ-check limitation, reducing -10% for REquires IQ roll to -8% for Requires IQ Roll (no FP on rerolls) but that's just randomly grasping for math