"Your salary is determined by how hard you are to replace. Scarcity creates value. Become irreplaceable" --
https://www.facebook.com/Nengieduhub/posts/pfbid0hYtZKK5j1SXk7R3UbGVDDqCQNKUnXfP8e2FvDPWHvT5PQiKiZ8t1T8KY2V7DyyfclNot true.
I was pretty hard to replace at my teaching job in Moscow in 2012-13. My set of skills was quite unique. It did not help me much.
Your situation is determined by how hard you are to replace for them versus how hard they are to replace for you. At my teaching job in Moscow in 2012-13, they did not believe that they would have to replace me, ever, no matter what. They did not believe that I would ever leave. They thought they were irreplaceable for me.
Your situation is determined by the alternative options that your employer has and the alternative options that you have. One side of this equation is not enough.