Um, JDM imports do them. They have them listed for $1300, so you are pretty close with the estimate.
I thought I saw the Mychron TG timer on the back page of the Motorsport NSW mag for $449.
So the simple lap time is much cheaper. On the other hand the driftbox tells you lateral & longitudinal gees, speed, drift angle, track position & some other handy features. Unfortunately it doesn't log rpm which is a bit of a silly omission. That lot will tell you much more than just a straight lap time or even a sectored lap time.