[paulcole]

How many people have you worked with who have required 2+ people to replace them when they left? Personally, in about 10 years "professional" experience, I've worked with 0.

I'm willing to accept that perhaps I've worked with non-exceptional people (I am one myself). But really consider whether your employer would actually hire 2+ people to replace you. Your domain knowledge is worth something and the cost of switching is high, but if your employer is paying below market, would they really pay below market for 2+ new people?

What I'm trying to get at is the fact that your perception of your value might be significantly different from your employer's perception. And if that's the case, you really don't have much leverage.