To stay safe in Windows 10 from next October you'll have to pay $61, then 'double every consecutive year for a maximum of three years'
Windows 10 is, I'm afraid to say, not long for this world. While Microsoft has confirmed that the ageing OS will still receive free security updates until October 14, 2025, after that you'll have to be part of the ESU, or «Extended Security Updates» program, and that costs money. Depending on your use case, that could be much more than you expected.