Give it a few days, price is inevitably going to rise. Even if you play 1 hour a day, for 30 days you can make 600k just by grinding instead of 300k.
I don't agree with any of this. Breaking the rule? What are you talking about? He simply found a way to trade membership since there weren't any other options implemented. I'm sure admins would remove his previous "How to thread" if it was considered a rule breaker. About him setting the price, he merely offered an exchange rate 2 weeks ago, membership price was/is more tied with coin store cosmethics than anything else.