YES, BACKUP!
My brother has an office with 4 computers. In November the big-bad-trojan
disabled two of his computers to the point they wouldn't boot in safe mode. He
was calling me saying - "Hey, I see a black screen. What can I do here? This
computer has all my employee files on it."
I said something along the lines of "Go f*** yourself and quit wasting my time."
I told him many times to invest $100 in an external USB Hard-Drive so he could
back up his files, but that was too much of an expense for him...
Listen - you either pay up front for the protection, or you pay two or three
times as much when shit hits the fan. And which will be a bigger loss to your
boss - the $120 for 3 computers for anti-virus and $100 for an external HDD,
or the cost of recovering data and replacing dead computers? I don't know
what type of files or information your company deals with so it's up to you
to decide if it is worth the investment.
He ended up sending the computers to Dell for repair, three months later, he
still hasn't received them back, and he has never recovered any of the data.