I think it is worth the extra - unless:
As has been pointed out, the Lee Auto-Disk powder measure comes in two varieties. Standard and Pro.
The Pro Auto-Disk and the Standard Auto-Disk are 100% interchangeable in all applications and installations. The bases of the units are virtually identical. In fact, you can convert a Standard to a Pro by swapping the hopper and a couple of parts. The only difference in the base unit is that the Pro has a teflon coating on the base unit and the Standard does not. They mount and operate exactly the same way.
The Pro has a round and much taller hopper than the Standard's rectangular hopper. Whether a larger, taller powder reservoir is more desirable is up to you. (Three and a quarter inches vs five and a half.)
The Pro has a Teflon coating on the main body. The coating is supposed to make the operation smoother and perhaps reduce powder leakage. I can't tell, but I think it may reduce the break-in time.
The Pro has a "wiper" part at the outlet of the powder hopper that is supposed to be kinder to powder granules and reduce powder leakage.
The Pro Auto-Disk hopper also has a valve that allows you to shut off the powder flow by twisting the hopper a quarter turn. The standard does not. Thus the Pro Autodisk allows you to take the powder hopper off the measure without emptying it. You can't do that with the standard auto-disk.
The feature that most people tout about the Pro is how the powder hopper/reservoir mounts to the base. Many users never remove the hopper, though, making it a non-issue for them.
The Pro Autodisk has brass, threaded studs cast into the bottom of the hopper and brass knurled nuts. Very durable. The Standard auto-disk has two small screws threaded into the bottom of the plastic reservoir. You can strip the threads if you are rough when removing and replacing the hopper. Very hard to repair, although, one COULD ream out the stripped hole, superglue a machine screw into the enlarged hole and then have a hopper mount very much like the studs/nuts of the Pro's hopper.
Both Auto-Disk powder measures use the same disks for meting the powder.
It is difficult to adjust for in-between powder drops. You can do it by reaming out a too-small hole, but once done, it is hard to go back. You would have to buy another disk.
So, here's the "unless" Some people, especially those who use the Lee Turret or Pro-1000 presses (which also have a turret disk that is easily pulled and replaced without removing the dies) choose to have a powder measure permanently mounted on their die set. Thus they have one measure for each caliber they load. The extra dollars can easily multiply while the benefits of easy replacement of the hoppers becomes less of a factor.
Also, the standard hopper is super-inexpensive as well as being cheap.