Just ducats or all?

The skill bonuses say just ducats, but someone changed the page to read exp, gold, ducats..

This will require testing. As ducat gain also effects how much exp and gold you get. So it all depends on if the commerce mastery boost is calculated before or after the experience and gold is.

It's calculated after the fact. I saw pictures with parenthesis showing a flat out 15% boost to each. The commerce exp formula doesn't work that way normally.