I don’t get the numbers on the chart for PS4 or Xbone, there are popular SKUs at less than $300 for both of them. PS4 has a 500GB version for like $260 or $270. Xbone S has been $260 or $280 for awhile now. Hell I think now you can get them for $250.
The chart is showing official MSRP (Manufacturer's Suggested Retail Price) for the consoles from what I can tell. The XB1 and PS4 SKU's you see that are selling for less than $300 right now are mainly discontinued SKU's or SKU's that are discounted temporarily by the retailer. The official price for both XB1 S and PS4 Slim right now is $300. Hopefully Sony and MS both officially drop to $250 or $200 soon.