Ticking time-bomb in the EDPB Guidelines on consent?

An old issue each privacy pro learnt by heart: “risk of negative consequences (e.g. substantial extra costs)” for data subject = no freely-given consent. 

Substantial. But what if extra costs are not substantial? What if, say, 10$ turns into 11$ if you refuse to consent? Is it ok? 

At leats, German watchdog seems to say yes. Some privacy pros agree (see below).

One can say that I am picky, indeed, 1$ or even 10$ surcharge will unlikely lead to bankruptcy. But what will happen if this practice becomes commonplace? Right, data subject will overpay every time he/she is requested to give consent. 1$ per one requested consent will turn into 10$ per ten requests. How long could that ‘receipt’ be a year after? 5 years after?

You got to the crux of the matter. While EDPB considers substantiality in the context of a one-off consent request, it does not address the aftermaths when overcharging becomes a rule.