Actually it is good for the south Korean to have THAAD defense system. It is because of the threat of North korea that they have a massive nuclear and ballistic missile. And you know kim Jung un the president of north korea is so crazy in nuclear activities. So it is so dangerous in North Korea. But I am not for the pay of 1 billion $ of THAAD because south Korea is allied of US.
I think that North Korea is having problems with the THAAD mostly because it is an American system. For example, if they purchase the S-400 systems from Russia, then the response from the DPRK will be more muted.
I very much doubt that after the bombing, the American base in Syria, which was guarded by systems S-400 there are not many willing to buy them. I hope that THAAD will be more effective. Any mistake can be expensive.
If the price will suit then the buyers will definitely be found. Never need to underestimate the enemy, who at the last moment have unexpected advantages.