They were going up before, during, and post ACA mandate, though. They've been on an upwards march alongside the underlying per-capita healthcare costs for decades. https://www.healthsystemtracker.org/chart-collection/u-s-spe... ("Total national health expenditures, US $ per capita, 1970-2022" - $2k/year --> $13k/year per person)

There were some pandemic era programs that increased the number of insured people, so it is possible things have changed since 2022. Either way, there is no evidence that the repeal of the individual mandate actually resulted in less people with health insurance.