Going have to disagree on the price of the 4k drive. 4k drives in the market cost at least $200+ and the good ones are way more than that. It will be a pretty big price cut. Even $100 off is quite a bit when you consider that means you can put those savings towards PS Plus, Game, another Controller, or any of the accessories. It's definitely not a "minor aspect" taking the cost from other similar drives.
It's also the reason back in the day the PS3 was so expensive. The Blu Ray drive was absurdly expensive and was the reason Sony failed in the beginning. They don't want to repeat that this time
Now if it's one of those cheap "4k upscaling" players then sure it's not that expensive but I don't think Sony would do that. They would get a lot of crap for that.