I get about 12K. But I'm not a gamer. For reference, on my tablet, I score over 20K. But that's a pen.
For my purposes, accuracy isn't about how fast you can get there, it's about how closely you can get to the target. I'm mostly a coder, but I do use the trackball for graphics work occasionally, and it's only bested by my wacom tablet in terms of precision and accuracy.
Oh, and I don't use the tip of my thumb to click. I use the base, instead. The whole piece to the left of the ball on the CST is a button, and I tend to click it near the bottom. But I never bother to take my fingers off the ball.