PLEX was designed as a 'legal' mechanism to undercut (and, for the most part, terminated) the black market trade in "cash for ISK" and the accompanying problems caused by automation of ISK farming by those black market sellers. It also serves as a mechanism for players to 'sell' ISK for 'cash', in the sense that they won't have to pay the real cash monthly fee if they sell their ISK (or other liquid property) to someone else for a PLEX.

It is not, however, an ISK sink. The only way to buy PLEX with ISK is to trade with someone who bought theirs with cash. That ISK remains in the economy and is not destroyed by the trade. The actual mechanism is hinted at early on in the article:

> The main way ISK is removed from the game this month was the purchase of skills from NPC corps on the market, with 13.602 trillion ISK sunk into skill books over the period.

This is wrong, based on the 2015 Vegas report: LP stores are also an ISK sink, exceeding - in 2015 - the skill books. Anyways, the above article links to:

https://web.archive.org/web/20150129024846/http://massively....

Which tries to explain this, but is filled with broken links to forum posts. I eventually found this post from 2012 that concisely indicates actual ISK sinks in the game in dollar amounts:

http://twostep4csm.blogspot.com/2012/03/its-econmony-stupid....

And their 2015 economy post includes a graph of ISK velocity ("the estimated number of times one isk is spent to buy goods each month, in this case a 30 day moving sum of total trade over total active isk each day") as well as the "total ISK" growth over time:

https://community.eveonline.com/news/dev-blogs/eve-economy-u...

And finally, it links to this chart, clearly showing the ISK sinks and faucets for September 2015:

http://content.eveonline.com/www/newssystem/media/68738/1/si...

In the sample month shown above, the amount of ISK in the economy increased from 870T to 876T (0.7%). This is not a significant level of currency printing - but currency printing isn't part of the definition of inflation, 'spending power' is. Fortunately, they also include the price of PLEX over time in this post:

http://content.eveonline.com/www/newssystem/media/68738/1/pl...

Estimating by visual inspection only, the price of ISK rose unusually quickly between June 2015 and October 2015, from 900M to 1200M, where it promptly flatlined. They decline to explain why this is - however, the current price today, over a year later, is 1300M:

http://www.eve-markets.net/detail?typeid=29668&limit=14#hist...

So whatever inflation occurred during that window of time has apparently returned to normal levels. Looking up the definition of hyperinflation on the Internet (I'm not an economist), the generally accepted definition seems to be a monthly inflation rate of 50% of the price of a given good, assuming a fixed spending power.

While it's impossible to say above with certainty that spending power remained constant, assuming that, the price of ISK would have had to increase from 900M to 1350M in one month to count as hyperinflation by the usual definition. There have been no indications that the EVE economy has reduced the spending power of its users, given their continuing efforts to feed users a steady trickle of additional ISK in the economy each month. So with the current price of PLEX one year later not yet having reached 1350M, it seems safe to hazard a guess that 'hyperinflation' - in PLEX, at least - is not applicable to their economy.