Understood. To me it's just a mental shortcut for trying to figure out how expensive it is for one platform to bring to bear an equivalent quantity of firepower. I.E., x number of 55s vs z number of other ships with the same theoretical output. A way of trying to figure out if the 55's extra cost is justified by extra capabilities that any number of 52Ds cannot match.
More broadly speaking, I am trying to understand why a more expensive 55 is preferable to a larger number of 52Ds or vice versa.
I don't mean this in a bad way, but I think it will be useful to not think about military capabilities in the manner you describe -- i.e. "quantity of firepower".
For example, in theory, if one was wanting to maximize the amount of firepower one could bring to a fight at the lowest minimum cost, then converting a few tanker hulls to arsenal ships loaded with hundreds upon hundreds of VLS would be the most extreme way of maximizing VLS count with minimal cost.
However, in reality there are force requirements that determine the need for having a given number of ships of various types and having a given number of ships to begin with (ultimately a ship can only be one place at a time).
The reason why one builds a 055 versus two or three 052D, or say a 052D versus two or three 054As or 054Bs, really needs to be considered in the totality of their costs, capabilities, and a navy's strategic requirements.
In a way, from that perspective it is easier to not consider VLS count as an important factor.