The break-even here is not a spreadsheet, it is a substitution question: does the suite replace spending you are already doing, or add spending for protection you already have free? Microsoft Defender is free, built into Windows and handles core detection on Windows, so the paid tool has to justify itself on everything except the antivirus engine.
Where the money comes back
A suite pays off fastest when its bundle absorbs other subscriptions. Bitdefender Total Security covers 5 devices and includes a password manager and a capped 200 MB/day per device VPN. If you were paying separately for a password manager or a light VPN, the suite's first-year price is close to a wash and the protection is a bonus. On Mac, Intego from $56.24 for the first 2 years is the specialist case, since Defender is not the Mac baseline in the first place.
When it is not worth it
Paid antivirus stops making sense when you are a single, cautious user on a current Windows machine with nothing to bundle away. In that case you are buying a second lock for a door Defender already locks, and the renewal makes it worse: Total Security renews at $109.99, so year two is the full price for protection you could have kept free. The boundary is coverage and substitution, not detection quality.
The decision rule
Count the people and devices you are responsible for, and the security tools you already pay for. If either number is more than one, a suite usually wins on coverage or substitution, and you should pick by platform. If both are one, keep Defender and spend nothing. Settle the free-versus-paid detail in antivirus versus Windows Defender, and price the second-year cost in the renewal-cost guide before you decide.
See what Bitdefender Total Security includes See Intego for Mac Or compare free Windows Security