Well that could also mean the Indy Jones set has a higher MSRP. But sure, I'm not in the business so what do I know? It just honestly feels like a waste and I'm not convinced they labels are gifting me free copies. It costs money supply the discs, insets and cases. They'd save themselves a ton by not providing them, especially since they're selling the Blu Rays struck from the 4K prints separately anyway. They would be biting into their own bottom line.
The cost to manufacture the extra discs, cases and artwork is either written off (doubtful) or added to the price (more likely).
Even if it's only an additional $10.
From what I understand, the costs to manufacture BR disks and the associated casing is almost negligible for these companies. The technology exists to just stamp 'em out and package them up very cheaply and quickly. You're paying for the movie itself (and any of the processes associated with remastering, etc) when you buy a disk, not for the physical material itself.
And the good news is that these are indeed vastly improved versions of the BR disks that were previously released, in that they are all full remasters and look gorgeous in comparison. In fact, if you look online at comparisons some YouTubers have done, there's not a huge difference between the new BR remasters and the 4K disks, but there is a huge difference between the new release and the old release.