Cost per transaction to the users is important, but it is mostly separate from the cost of mining. The cost of mining is dictated by the price. Conflating the two doesn't make sense, because they aren't correlated and the costs are taken on by different groups of people.

Not only that, but not all cryptocurrencies are even trying to optimize for this. I would say that bitcoin is actually in the opposite direction and trying to be as expensive per transaction for both the miners and users as possible.