True, I would in most cases call a computer a tool. Different usage requires different maintenance, and for general maintains I do not think antivirus offers a good value compare to alternatives.A reasonable argument and I would agree, but I think as a community we should refrain from calling a Mac an investment because, to be frank, I believe that most people aren't buying a new computer for "work" or producing more value than the cost of the machine.
1. viruses and maleware are rare for MacOS, one often have to look for it or visit suspicious sites.
2. Using timemachine and cloud solutions offers a fast way to reset the system to an unaffected state.
3. Apple has some good build in security measures, people should just enable them.
4. programs like Little Snitch (I am really fond of that program) which allows to control what communication you Mac is allowed to do