Is it illegal not to include the group purchase fee in the purchase contract? = = Who did you give it to? Is it the developer's? I don't think the developer will accept your money, but the intermediary should, so you can't ask the developer to write it into the contract.

As for breaking the law, the definition of personal feelings may need to be discussed. You must have known something about how group buying works before. Now that the contract has been obtained, it's a bit late to forget about it.

There is not enough reason for you to check out.