They are possibly illegal or at least against the law's spirit, which is ironic, because Heise is a relatively well respected publisher among German IT professionals.
I think they are legal because the requirement is that you have an option to "deny all" which they provide. That you must subscribe to the "Pur-Abo" to use this option doesn't matter.
I am p sure that not too long ago the EU Commission put out a statement regarding Metas "Consent or Pay" and it not being allow and "privacy isn't something you should need to pay for". So I don't think its legal, but I also didn't look too much into it other than some headlines.
I don’t think that’s right. You can’t force someone to pay to not have tracking cookies (or something that infringes on the right to privacy). Facebook tried the same tactic and was forced to stop.