If your standard income is high, it is always more advantageous to make National Pension additional payments after retirement

If you opt for voluntary continuous coverage after retiring at age 60, it is more cost-effective to make additional payments based on the median income after retirement rather than the high income standard applied while employed.
I didn't know this, so I recently made additional payments for 30 months totaling about 1.9 million won [sic - context implies 19 million won]
Even if I get 4-5 million won in income tax deductions, I could have settled it for 10 million won after retirement.
As a result, I think I lost about 4-5 million won.
Over-relying on what this ChatGPT fellow said was my mistake.