It is not illegal for the person paying the money in most cases. He is not party to the agreement so he cannot break it, many times the buyer may not know such

It is not illegal for the person paying the money in most cases. He is not party to the agreement so he cannot break it, many times the buyer may not know such an NDA even exists. It is different for the person breaking the NDA. In some jurisdictions it only civil crime, it could be criminal as well especially if other acts like insider trading are related etc. Whistle-blowing protections are a patchwork today, A lot depends on whether you are blowing to a regulatory authority or a established media publications etc. Also how/what you share and how you got it(breaking CFAA is illegal) makes a big difference as well, also being illegal does not mean you will necessarily get prosecuted, it could be bad optics for either the DA/AG (in case criminal) or the company(for civil) to sue - Facebook as yet has not sued Haugen although they clearly have a strong case for example.