Why OpenSea is asking me to sign a transaction and pay a fee for setting royalties?

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I set up my royalties on my Manifold contract and I have added the Operator for OpenSea:

But when I go to OpenSea collection to setup the royalties I am asked to sign a transaction and to pay a fee. This never happened before, is this a new way of doing things or is it something wrong with my contract?

Thanks.