MTGNexus

So, here's an oddball that came up recently:

Disparaging Wealth -- B
Enchantment {R}
If the effect of a spell or ability would cause you to pay a cost, you may pay that cost an additional time. If you do, create a Treasure token.

Is this the correct / best wording?
Does this break any cards? I suppose it has some weird combo potential, but nothing leaps out at me. I'm probably overlooking non-mana related costs.

Three things come to mind:

• I think this should be a 'whenever' and create a triggered ability. The 'if' clause makes this read like a replacement effect, which feels incorrect.
• The 'would cause' text is weird. There are only three cards that have that wording, and two of them - Rain of Gore and Unpredictable Cyclone - have very deterministic causes and replacement effects. In contrast, something like Mana Leak doesn't directly cause someone to pay a cost - rather, they are given the option to pay the cost, which they may or may not do.
• I also feel like you may want to specify what types of spells / abilities you want this to apply to, since it's pretty open-ended. Do you want paying life for a shockland to trigger this? That is an ability which creates a replacement effect that costs life. Leonin Arbiter probably also does something weird with this.

I would word it as:
"Whenever you pay a cost as part of resolving a spell, activated ability, or triggered ability, you may pay that cost an additional time. If you do, create a Treasure token."

"as part of resolving a spell" is what is called a "spell ability".
Also, to keep this in Black's share of the pie, I would also limit it to nonmana costs, so it works with life payments and creature sacrifices.

Whenever you pay a nonmana cost of a spell you cast or an ability you activate, you may pay that cost an additional time. If you do, create a Treasure token.

Or a simpler (and more Black), but a more restrictive variant:

Double the nonmana costs you pay.
Whenever you pay a nonmana cost, create a Treasure token.