That trend seems to be over. China's antitrust regulator has put the DRAM cartel on notice, and they're willing to stand up state-sponsored fabs to deal with it if necessary. Coincidentally just after that, Samsung announced production is going up and prices are expected to decline over this year.

http://www.china.org.cn/business/2017-12/23/content_50157479...

https://www.theregister.co.uk/2017/12/21/china_memory_insour...

https://www.reuters.com/article/us-samsung-elec-chips-outloo...

Pretty blatant market manipulation here by the DRAM cartel - and China has enough downstream manufacturing at stake here that they're willing to go to the mat over it.