I had to learn:
"If you pay peanuts, you get monkeys."
"If you buy cheaply you pay dearly."
First, we’d like to say that jHackGuard doesn’t have a paid version. It’s a free plugin designed to improve your site’s security.
As to your site being hacked over and over again, we’d advise you to get it checked by a professional and make sure that there are no backdoors left from previous hacking attempt.
Having a secure website is a combination of following good practices, having the proper software and keeping it up-to-date. Unfortunately, you can’t have all hacking threads neutralised by using only a single plugin.