As per the title...

Many forum posters have put forth the conceit that 4k capable Blu Ray drive is a substantial cost,
specifically Kerotan has put forth $50 as the extra price of that feature (vs. standard Blu Ray),
some posters have even put forth higher numbers than that, I beleive.
Clearly, this claimed higher cost has been used to justify non-inclusion in both Pro and Slim revisions of PS4.

This thread is for substantiation of that claim, i.e. discussion and evidence of actual OEM bulk order costs.

AND for dicussing it's implications, which seem spectacular to me:

Because if the additional cost is $50 as claimed, that would seem to mean that either
MS is subsidizing Xbone Slim to the tune of $50/unit to achieve price parity to PS4 Slim,
or Sony is actually just making $50 pure extra profit/unit for each PS4 Slim sold...

Thoughts?

It's probably less than $50, but there are more than simply raw manufacturing costs involved. Unit sales, shipping, and currency exchange rates all come into play as well, and right now the yen is extremely high for Japanese exporters, hovering around 100 yen to the dollar since the Brexit vote. Without more data such as that, it's very hard to speculate what the extra costs could have been. Hell, MS might be losing a bit of cash on the slim in order to build up hype for the Scorpio.

Good question, I want to know that too

The weaker, cheaper hardware probably allows MS to include a 4k player at the same price point.

What about the cheap addition of a HDDVD drive too, or a laserdisk drive? wouldn't cost much to add, that said, how many times have people actually used the blu ray function of the ps3/4 is it a large % of the userbase if not then why does it matter that they didn't add another drive function instead went with pure $ to power instead. No idea why there is so much tears about this, maybe Blu ray collections are a huge thing and I'm just completely after missing out since I stream my media to the ps4.

I read that the total cost of the PS4 slim was roughly $200, so that would be 33% margin.

I personally think MS is taking a loss on them just to make it look like an attractive product for the price, I keep hearing this supposed $15 dollar figure for including the parts thrown around, but that doesn't seem likely. Once this quarter's up, we're going to see some staggering revenue loss on the Xbox division's part.

I don't think the money is a concern though. MS just wants to keep the brand going until Scorpio launches. They're never going to make money on the hardware, but they don't want the division to die either, so they'll take the hit.

I don't understand what you're saying.  Are you saying the weaker x1 slim cost as much as the ps4 slim and therefore the only difference is the blu ray player?

My opinion is that Sony is making more than $50 / PS4 slim while Microsoft probably not a penny on their own slim because of the bigger overclocked APU, bigger motherboard and UHD drive instead of bluray one.

I think Sony will lower the price of their slim once all the 1200 models will be phased out, probably starting this december, maybe temporary only. Finally I think Sony must not make a profit (or very small) on the PS4 Pro and the $399 price is there to stay for a long time, no temporary price cuts for the Pro for the next holiday either.

We are talking about 1:1 replacement here, so volume is the same, shipping equally applies, currency exchange equally applies.  
I'm not saying those aren't factors in the cost, but they are going to apply whether you order a shipment of high spec or low spec drives.

This topic was covered when Xbone/PS4 were introduced, basically MS' architecture means they spend CPU (APU) die space on memory,
while Sony can in the same (or less) area have actual processing transistors, with MS thought to have marginal higher costs AFAIK.
If you want to account for this difference (in either direction), OK, but please use a solid figure as debate of that is tangential to thread.

This thread is not about whether you or anybody else LIKES the feature of UHD Blu Rays, it is about the cost of that feature,
which MS is including in their Xbone Slim, but Sony is not including in either their Slim or Pro, and assessing cost impact of that.
If you don't like UHD Blu Ray then the cost of including that feature (or not doing so) is just as relevant as if you do like it.