In the United States, PSN discounts for PS4 are usually pretty big, and depending on the time they are usually lower than most physical retail (like if you order Amazon or Best Buy, etc.). The one exception would be GameStop, which sells used games based on a trade economy (most people are super ignorant of this... for every 'bad' trade you think you're getting, you could be buying games that are only a few months old for ~50-75% off...).
Because the PS5 has little to no exclusive games, they've decided to start selling "PS5 versions" of existing PS4 games - THOSE are marked up in their store. You can still buy the cheaper PS4 versions and in most cases play them on your PS5.
As for this sale this post is about - there is nothing significant about it. Sony has at least one big sale every month, and around 50% of it will be really good deals. It's not like Steam where they put everything at the lowest price point twice a year. It's more like... PSN has 1/3rd of games on sale one month, 1/3rd the next month, and so-forth rotating, with developer-specific discounts sprinkled in. Last month's sale was incredible, even devs that only have sales 2 or 3 times a year (Square Enix...) had everything on deep discount.
SOURCE: Believe me, I am one cheap-ass mf'er