Interesting numbers. What comes to my mind, however, is how much work you are getting done.

If your single speed pump is sized correctly to your filter and pool, it should do the job it's intended for. For a 2 speed pump to do that same job, it would need to do it at low speed for you to realize the cost savings.

So a 2 speed would benefit you only if you need the high speed to accomplish a task other than filtering. (Which, of course, would be quite frequently for many pools....but not all) Otherwise, you could simply use a single speed of the same power as low speed for adequate filtering.

After all that, running quietly and efficiently are big, big pluses for 2 speeds and I believe they are a good value. I'm not sure the cost savings is as dramatic as it might appear.