Says who? Apple is already overcharging for the SE's design. And even if the price increased, if that translated into much better battery life and a modern looking screen with Face ID, I think Apple would be rewarded with more sales. At $429 it's the cheapest iPhone with the A15, yet Apple still has to cut production.And then it goes from a $429 device to a $629 device.
I think that the translation is this: customers aren't exactly excited for the same old recycled iPhone 8-era design from several years ago, thick bezels, coupled with a poor battery. If you put lipstick on a pig it's still a pig. It's time for Apple to make the iPhone SE modern and improve battery life.
The market is voting with its wallet and that's a good thing. It's a strong signal that Apple needs to find an innovative new design to incentivize customer demand.