Why is cost threshold for parallelism ignored?
Anyone ever see Cost Threshold for Parallelism being ignored?


It is not being ignored. During the compilation process, the optimizer first considers a serial plan. If the estimated cost of that plan exceeds the Threshold, the optimizer goes on to look for a parallel plan. If the resulting parallel plan is costed below the best serial one, it will be chosen.

So, the parallel plan will have a lower cost that the serial one (which you cannot see). It is perfectly possible for the final parallel plan to have an estimated cost below the Threshold - the point is the best serial plan candidate exceeded the Threshold.

An example can be seen in my blog post on parallel plan bitmaps.