Disclaimer, I am not any expert, just preventing those who care to don't make the same mistake. If you don't care, there is nothing here for you :)
Context: I have started my 4K UHD Blu-ray collection, I went from zero around 3 months ago to have around 70 Blu-ray now which 97% are 4K UHD and a region-unlocked Panasonic DP-UB820 from David Gatti Audio.
60% or so of them were from Amazon UK, then JB Hi-Fi.
During Prime I got a few more from "Sold by Amazon US" but let me tell ya, what a regret. Amazon US sells the thin case Blu-ray, even the ones that comes with 3 media (4K + Blu-ray + 3D) have the thin case.
It is weak, the locking mechanism to keep the media in place breaks, the packaging shows sign of being "bent" at some point but not enough to break the media. If it is single media, it is even thinner like 50% of a normal Blu-ray case.
Add to that, Amazon US delivers it with a bloody plastic bag, that explains the "bent" close calls. Amazon UK uses a cardboard envelope alike, it is hard enough to protect the media and all the cases are full format, the normal thick case you would expect.
I received The Batman today from https://www.ozbargain.com.au/node/870108 from "Sold by Amazon US". As expected, thin case, there are 3 media from which 2 were loose and the locking mechanism to hold the media in place is broken, I do have empty full profile Blu-ray case.
Prior to Prime Day, I had noticed this, but I totally forgot about it.
So anyway, I don't think the bargain is worth within this circumstances imo. I am only buying again if from Amazon UK, they are solid.
Good to know sir