It's not high, it's insanely high.
Let's say there are 4 thousand idols actively promoting in Korea (I believe the number is actually much lower than this). 1 death per thousand people is an absolute disaster.
The country with highest suicide rate in the world is Lesotho, with 0,87 deaths for every 1 thousand people. Heck, Korea itself has a rate of 0,21
kpop idol suicide rate is not that much different that hollywood celebrity suicide rate.