Let's say you get 1 real email and 30 spam messages per day, and you spend
two minute to go through these. This time involves downloading them and
possible deleting the spam messages. It also involves checking your spam
folder to see if anything seems like a real message that is mistakenly
taken for junkmail.
Let's say you earn 15$ per hour. Spam is costing you 50 cent per day.
So in one year you have spent 182.5$ fighting off spam in your inbox.
Or 12,6 hours in one year sorting junk email.
These figures could be more or less, but it gives and estimate. The point
is that even if you think you can delete the spam very fast all the little
spam messages eats your time in the long run.