That’s not true and you can verify this yourself. Go to Adam4EVE and check the price and volume history of PLEX:
I’ve added some commentary to the picture to highlight the impact of demand and offer on the price.
This has little to do with bots or “super players” controlling the economy. Rather have many players stopped selling PLEX into the market since September 2018, which then started the price climb. This may have been caused by the previously falling PLEX price.
If anyone can remember it, we had a thread or two about the price of PLEX being “too low” back then. And as of January did the demand then increase and caused the price to shoot up.
So now we get the counter threads, where players complain about the price being “too high”.
Also note that just a few days ago did around 500,000 PLEX appear on the market, which immediately put a bump into the price climb and shows how quickly and actively things can change in EVE.
Always keep in mind when you buy PLEX that another player has been paying for it with real money just so that others can play for free. The price is controlled by demand and offer and players will only sell PLEX into the game, as well as buy PLEX, when they believe the price is right. The price of PLEX is not fixed but in control of the players.