Note 2: In Eve, the ISK (gold) value of a PLEX has NEVER gone down. It increases on a regular basis, but the price of a PLEX in real money stays the same, thus effectively lowering the value of the in game currency
It has actually, CCP (the company producing EVE) has an in-house economist that occasionally floods the market with confiscated PLEX from people caught RMTing forcibly driving the price down in an attempt to keep it manageable.
In fact, the price of PLEX in EVE is down about 7% from 6 months ago; however, it still costs about 250% more than it did when it was first introduced years ago. It's not really a fair comparison though since the WoW-token will be price fixed based on market data, and purchased tokens from the AH will be soulbound. In EVE you can 'control' (or at least influence) the PLEX market if you have enough liquid isk.