Its sounds so minimal price difference. I think It will be 100 minimum
Sure, a 500 dollars difference. They will give you the discless version for free. xDD
Now seriously: by selling the normal version at $500 they are already losing money, that later they may compensate with Plus, Now, and selling ~10 games on average per console at the end of the generation. $50 cut could be possible by reducing $15-20 by removing disk drive related stuff, considering that out of these ~10 games sold per console 4 or 5 would be full priced AAA games purchased digitally instead of in retail, which I think it's too generous because many games already are bought discounted, digitally or are cheap indies.
Even without considering the discless SKU the % of games that are being sold digitally increases year after year, so it's going to be hard for them even to justify that $50 price cut. I think it's going to be very difficult to see them cutting it beyond $50, and if they do it, won't be more than $100. I think the maximum possible difference, even if they make an extra effort on top of the one they already will do with the normal SKU, is $100. Something like $399 and $499 or $449 and $549. But again, my bet is $449 and $499, and my second bet woud be $499 and $549.
I think the discless version will be about 100$ cheaper, because long term Sony would want to push a discless System in favor of digital sales.
So even if the drive adds only 20$ to the bom, I think they want to give people an incentive to go digital.
Just a theory..
Companies aren't charities, they need to justify costs and target profits even if it's a long term with decent estimations. PS4, like the consoles who sold the best ratio of games per console, sold an average of around between 10 and 11 games per console.
Very likely a big portion of these are cheap indie games, discounted big games and digital big games. We know that year over year the % of games sold that are digital is growing so very likely will continue growing. As of now it's around half of the console games sold so at the end of the generation will be already pretty big even without considering the discless SKU.
A $50 cut would assume that on top of the $20 saved because of the disc drive and everything else related, in games 4 AAA fully priced retail games sold for these console owners should be replaced by 4 AAA fully priced digital sales. Which isn't too realistic, seems that it would be more likely to consider 2 or maybe 3. But well, let's say that 4th game could be compensated by a slightly increase on Plus and Now subs for the digital only SKU, if that is the case.
So I think a $50 price cut is already a difficult and risky long term bet, and $100 would be too much. Specially considering the uncertainity caused by the financial crisis, jobs losts, companies shut down and death toll caused globally by pandemic.