It is pretty low at games with experience loss standard (it was possible to lose weeks worth of grinding at near-max levels in a different game I did play, and losing "only" 1-2 hours at mid level meant you were really good and/or in a fine party), but it is quite high for a game that generally does not have experience loss.

That being said, there was a warning. And everything other than the amount was stated. The loss itself is just a bad design that was always used by free to play games to make no-loss items (or experience boost items, or both) to get money from their item mall.

A subscription game should never have implemented it in the first place. Though I'm pretty sure that there are others that did, if not most of them, which just shows how generally anti-player developers tend to be.