Possibly the following:
- Happier customers
- Additional positive news coverage and better PR
- Customers buying more games (and sending more money to Sony) instead of putting money in scalpers' pockets (in addition to the commission fees pocketed by eBay etc.)
- New players who can't afford the scalpers' excessive markup but might become long-term PlayStation customers if they could just find a console at MSRP
I almost wish Sony had offered PS+ subscribers the chance to preorder a console that would be factory locked to their PSN ID for a year or something, sort of like a phone upgrade.
Fortunately Sony seems to have a better availability track record than (cough) Nintendo, so I expect that the supply will improve fairly quickly. Also since many transition games work on PS4 as well as PS5, there's not a huge downside to waiting.
If anything, Sony will see that given the demand, they could probably sell the consoles at a higher price in the future.