Sony have made cost savings on nearly every major component of a console.
APU, the biggest cost sink of any console is APU, Series X has a 360mm2 die and it is housing 44% more CUs. Sony's APU should be around ~300mm2 which gives them ~15% savings on the cost. Accounting for node if Series X SoC is going to cost ~$175 to manufacture, Sony are saving ~$25-$35 on APU.
RAM (main area where prices have shot up), while both have 16GB of GDDR6 memory. Microsoft are buying 2 more 14Gbps modules compared to Sony who are buying 8. Plus Microsoft are also spending more on a wider memory bus. Sony are again saving ~$25-$30 here.
Storage - This is difficult to gauge because Sony are using 12 lanes and attaching them each with a small storage module. Microsoft are using 4/8 lanes but attaching them with bigger storage module. These storage modules don't come cheap with size so it could be a wash out. Also, keep in mind what's making Sony SSD so different is a bunch or I/O customization they have done on the die itself. As for the actual setup, Sony are building their custom I/O controller which should save them few precious dollars.
Cooling and other peripherals like controller, Sony's cooling solution according to patent is unique but Microsoft themselves are using a huge vapor chamber. I doubt rest of peripherals would vary much. But, lets assume they're spending $10-15 more here.
Accounting for all of this, Sony are saving to the tune of ~$50-$55 which is where Bloomberg article (BoM $450) and ZHuge pegged it. That difference might not sound much but remember every additional $10 they eat on BOM cost them $100m for every 10m units sold.
Finally, guessing MRP on basis of BOM alone is a fruitless endeavour given other factors which make the pricing very delicate. Most important being position and price of competitors product. Keep in mind Microsoft are planning to launch with a lower-spec machine at $249-$299. Sony have to price the PS5 correctly to undercut both of Microsoft SKUs, one at power, other at price. A ~$50 savings on BoM puts them in a stronger positon to make the necessary call of eating bigger losses (than intended) at launch since they wouldn't be as substantial in the long run.