There is currently (and for a few days now) a glitch in the WebAssist Upgrade system.
Any 'dot' release upgrade (i.e. 1.1.7 to 1.1.8) should be free.
I have in the upgrade section in my account an invitation to upgrade SecurityAssist for $52.49. I already own the latest Security Assist (1.1.8)
If it were me, I would contact Sales directly for a refund. contact-us.php