I think it's for the same reason why car manufacturers don't like it when dealers sell over MSRP; it hurts the long term customer relationship. Higher MSRP means fewer buyers which means fewer services, repairs, etc.
More expensive consoles means fewer owners, fewer people buying console games and subscriptions.
The usual price cycle is MSRP at the start of sales, then a few sales at some retailers, then slowly "old model" sales, when a new model comes out, and finally "final sales", when they're trying to get rid of the stock, and we all know and expect that.
If you buy a car for 50k, and it's 30k 6 months later, while still being a new model, you feel screwed by the company, and next time, you'll delay your purchase until the price drop (even if the price is a good price and won't drop). As before, if the price drops after a new model comes out, people understand that, but if the price drops regularly after a few months the product is out, that's a whole different story.
These retailers are selling much more than just the PS5. The customer relationship matters a lot to them. I doubt sony would let them upcharge even if they wanted to anyway.
Right, the console isn't the source of most of the revenue (or any, some have been losses). The point is to get them being used with newly purchased games/accessories. The scalpers are actually taking money away from the console manufacturer for the period of time the console is held by the scalper. They're also scalping revenue off the top of the console and having a negative income effect upon the end user/customer of the console - which definitely negatively affects how much the end user/customer winds up sending to the manufacturer.
I think it's for the same reason why car manufacturers don't like it when dealers sell over MSRP; it hurts the long term customer relationship. Higher MSRP means fewer buyers which means fewer services, repairs, etc.
More expensive consoles means fewer owners, fewer people buying console games and subscriptions.