If you have already added new Gelato products to your Squarespace store or if you connected existing products or variants to Gelato, the retail price can be only updated from your Squarespace store.
You are also able to bulk edit multiple products at the same time. You can read more about editing products in Squarespace's Help Center article Editing Products.

Currently, it is not possible to change the retail price of your Squarespace products from Gelato.