If you think people don't get banned for saying "kys" then you are sorely mistaken, as there are countless threads and posts in PB alone of people who were banned for telling someone that. In fact, here's a recent example of that happening.
That aside just like in life you aren't gonna get an infinite number of chances to improve your behavior, and if you've shown time and time again that you're more interested in behaving inappropriately than you are anything else then eventually you are gonna get removed permanently. LoL is no different: if you've shown time and again that following the rules and keeping your account isn't as important as behaving inappropriately then regardless of money spent you deserve to get permabanned. It's unfortunate but you had your chances and you blew them, so that's on you not Riot.
Now if you would like to actually discuss your ban then please post your entire unedited reform card here in this thread.