I watched a review that stated that the increasing cost of the cards only depends on the cost of the first card on the right.
E.g. If the first card on the right costs 3, then the others cost 4, 5, 6, 7 irrespective of their printed cost/value.
I checked the rules and the definition doesn't seem very clear.
I never saw anything like that. For me it was always the cost plus the modifier on the market.