I'd disagree with this.
The PS4 wasn't even supposed to launch at $399. That was a last minute change Sony went for once they caught wind of the Xbox One being $499. The playstation camera was axed from the box to hit the $399 price point, and done so quietly in order to maintain that $100 advantage.
This was coming off of the PS3, Sony's weakest selling console ever, and with Microsoft still being the dominant player in the US. They were confident up until the last second that the PS4 could be sold at a higher price than $399.
The PS5 is in a FAR stronger competitive position, and vendor lock in means few gamers on either side will be switching platforms. From a marketing perspective, there's no reason to skimp on hardware and cut out features to hit the $399 price point- the PS5 will sell out regardless. There ARE several reasons to build the best machine they can at the price the market will bear, though.