Amazon has dropped the price of the 4K version to $33.49 as of the time I'm writing this. The new Blu-ray version without the 4K disc is still stuck at $39.99. So, for the time being anyway, it's actually less expensive to get the 4K disc than not.
All those new extras sound wonderful. I don't need 4K, but I might buy this just for the more extensive extras than were included on the original Paramount disc.