Some Blockchain startups are coming up with ideas on how to solve a marketplace of data, but I fear it's not enough yet and it will die down with the ICO craze.
The big problem right now is that Cambridge Analytica/Facebook are about to set a precedent for large-scale data misuse by receiving little to no punishment. In a fair world you'd be right, and regulation would exist to give Facebook and co a big enough fine for their breach of trust to ensure that no one ever does this again.
The other problem to consider with GDPR is that it might set a barrier to entry too high for potential competitors to Facebook to emerge, which on the other hand has enough money to comply/pay the fines right away.
Yes, it would still be profitable, the only thing I'm not sure about is if the fine would be cumulative for every misuse instance (i.e. in the Cambridge Analytica situation, 50M * 4%WGR) or if, every time a misuse is found, it's a una-tantum fine.
Might also be FUD to force countries in the EU to regulate tax at the same level, but I doubt Ireland/Holland will go down without a fight