Historical Rules · 20 November 2020
Rule 607.2i
Official source text from the 20 November 2020 Rules release
If an object has an ability printed on it that causes a player to pay a variable additional cost as it’s cast and an ability printed on it that refers to the cost paid “as [this object] was cast,” these abilities are linked. The second refers only to the value chosen for the cost listed in the first as the object was cast as a spell. See rule 601.2b.