It is just market correction. If there would not be a chinese invasion, PLEX would be around 3,5-3,6 now. Freee market means it always demand and offer. Offer returns to same values as before chines migration or a bit shorter. Because now I do not need to sell 750 plexes to buy a 1,5 billion ISK toy, I need to sell less, than 500. Demand is higher, because CCP keep selling more and more new stuff for PLEX (new skins, skill extractors etc) instead of ISK. And also because all those, who payed real life money to get into rorquals want to cash their ‘investments’ back. Null sec accumulated so much ISK, that it would take World war bee second edition to make those money move instead of being stored in PLEX.