I have don't recall ever seeing them on sale, however they are worth the price IMHO. I' purcheased D4 in the 90s and have yet to upgrade the parts to the pro version. The design is excellent as is the build quality. Leigh has probably the best documented user manual of any tool that I have ever owned. They company is excellent to do business with, spare parts are readily available and I have built many projects with it over the years.
There is a learning curve to using it and requires some practice to get the jig, and your skills, dialed in initially. It will be worth the effort. I highly recommend the vacuum attachment/router support as it works wonders. Take a look at their many instructional videos as they are well done.