(b) is allowed. This has been confirmed by the Austrian Data Protection Agency. (I haven't checked other DPAs, but they coordinate with each other.)
In the case above, a newspaper offered access to paywalled content for a small monthly subscription fee, and readers would consume it with zero ads, zero tracking.
Alternatively, they offered access with no monetary cost, but instead in exchange for tracking.
The DPA ruled this as fair because readers had a choice, and because the paid model was reasonable for a newspaper subscription (€6/month).
The key here is that starting with alternative (a) makes it a paywalled service, which is clearly legal (think Netflix). Also offering (b) just offers another mode of payment.
You wrote earlier: "GDPR breaks the normal monetization methods of the web." Well, smoking regulation broke (some of the) monetization methods of Big Tobacco.
Arguing against the GDPR here is besides the point. The GDPR is not an end, it is a means. The end is recognition of right to data as a fundamental right.
Re-writing your statement in light of this, the point becomes "Data as a fundamental right breaks the normal monetization methods of the web." Opinions will differ here.
