We say that a worker in a business will spend the same amount of time
fighting spam. The business have 50 persons reading email. That adds up
to 630 hours for this particular business. How much these hours are worth
is a bit difficult to say. First you will have to pay for the workers
to sort and read the spam. Then there is cost of production machinery
and other operating cost during the time that these are not utilized.
Then there is the loss of profit. A guess could be a total cost of 35$
per hour. It adds up to 22 750$ per year. This is a very uncertain estimate,
you can probably do even better your self with accurate numbers.
When you rely on email for business communication it is important that
you do not loose legit emails in between all the spam. If you miss emails
involving big deals, you will loose money. Not just the cost of every
day waste of time sorting out spam.