Like you say, the PLAN has to take into account the exact same costs...
The govt can use state ownership to offset the cost, but that only means moving the bill to someone else. Economies of scale can help alleviate some of it, but has less impact than what might think. Look at the USN submarine fleet, even after 40+ SSN, the price isn’t that different.
My point is just that having a large SSN fleet could be economically unfeasible, especially if the large SSK fleet is to be maintained at the same time.
Or it might be economically feasible, depending on how much the PLA budget may continue to grow (especially if it seeks to match the defense budgets of some other nations like the US in terms of % of GDP).
However as far as capability is concerned, SSNs are very much appropriate for the PLA's likely future defense strategy. A capable and potent SSN force is as useful for conducting open ocean anti shipping and submarine hunting missions into the western pacific that SSKs are simply not capable of doing. Not to mention of course being necessary to escort Chinese carrier battle groups and other large naval formations as well.
This is leaving aside the various other functions like longer range surveillance, land attack/strike, mine laying.
Basically, compared to SSKs, what SSNs offer is much greater range and endurance and much greater cruising speed and top speed. That in turn dictates where SSKs can competitively operate in and where they can't. For more open ocean missions whether it is hunting opposing SSNs, trying to hunt opposing surface ships, or escorting friendly surface ship formations, SSKs simply will not do.