wasn't people already saying the price of the SSD expansion because they were out?
Yup, people were dreaming up more shit, the sony fanbois are really good at finding nuggets of information and piecing it into the thing that PS5 SUPPORTS and they're 100% confident of it(the people grabbing random Sony 3D sound tech that's in phones and trying to claim that it's what 3D Audio "is"), when in reality they've got a snowman made of shit... a shitman.
Sony is probably running intense tests on a few SSDs to make sure they don't make the machines die in an awful fire, or more realistically negatively impact the thermal performance.
Don't be shocked if PS5 CERTIFIED drives are the pricier ones, I'm not saying that because they've certified them, I'm saying that Sony isn't taking any risk on jank brands in their machines.
I think M2 is advanced enough that Sony will be possibly able to REJECT a non-certified drive if it's stuck in the M2 slot and have it not work at all.
TL;DR: If you want an SSD to expand the space HOLD YOUR FUCKING HORSES ALREADY FFS, it's coming, but it will take time.