Those kind of fines are simply not compatible with low quality advise like “Just add an opt-in checkbox, and you’re good to go for GDPR! What’s the big deal?”.
Overall, I like GDPR a lot (though as a disclaimer, I should say I haven’t read all ~80 pages yet).
Still, I am not as confident as many here that GDPR will have no serious unintended side effects.
Imagine for example if Google, Microsoft, Facebook, etc. all get hit with huge fines despite genuine best attempts by them to be compliant, after which they decide to cut their losses and exit the EU market entirely. Stock markets could crash globally, a new recession would occur, etc.
I very much doubt anything like that would happen, of course. But until things settle post-GDPR, I don’t think anyone can say for certain how this will economically affect the EU, and the world.