With ACA being generally accessible, how can a 50 years old person with cancer incur in yearly health expenses higher than premiums + max out of pocket? Or is s

With ACA being generally accessible, how can a 50 years old person with cancer incur in yearly health expenses higher than premiums + max out of pocket? Or is such amount, which heavily depends on your income but should not exceed a couple $10ks a year (and would go down significantly if you have no income), what would cause you to sell your house?