@Milk Speaking about this game, I think it's already out of control: if some items are being sold for what an average user playing 3 characters earns with ~166 weeks of weeklies without spending a single meseta, then there is something wrong with the game's economy and those playing the market (willfully catering to gold buyers).
While I generally would agree with you that those that bought low priced items do not deserve to be permanently banned, in this case SEGA has warned several times to not do it.
I understand that not everyone reads the forum/website/twitter, but the warning regarding what was going on with shop (with a link to the website) was also presented in game, so SEGA did all they could to reach players.
Bear in mind that people lie all the time too. I remember when I was playing Archeage, botters organized themselves on a forum with all sorts of excuses (it was my brother/sister, I got hacked and such) for their appeals.
With all that in mind, you should realize that it is hard for someone reviewing your account to understand the real intentions and going through each and every appeal is time consuming, so I guess SEGA decided to perma ban everyone and call it a day.
At this point I don't think it will solve the real problem (inflation), I can only hope that they will handle NGS better.