Pretty sure the pre-order pricing is $29.99 per book. I assume that’s the pricing model, although I suppose it could change. If you already own the PDF through Paizo, you get a $10 discount on the owned book.
I’m not clear on exactly what unserved niche it will be serving, or what it’s even competing against (aside from being the PF version of D&D Beyond). What will it do for me that I can’t already do, or what will it make far more convenient for me?