Gross, wilful, intentional, deceptive non-compliance. To be honest you have to put quite a lot of effort into managing to get fined for non-compliance with EU regs/dirs.
EU directives are transposed to member states, who are the ones who enforce EU policy. If you're talking about EU members getting hit for non compliance with directive implementation - sure. If you're talking about private sector non compliance with transposed EU directives, that's largely up to how individual member states enforce EU requirements, since EU directives effectively become separate laws once they're transposed by each EU member.
As far as I'm aware, there's little aggregated data on how individual member states enforce (as in, number of cases and total amount of fines per year) EU directives. The EU takes in ~4-5 billion Euros per year in assessed fines, but the total amount should be significantly higher once you account for all of the cases/fines that are assessed on private companies, by individual member states, for non compliance with individual state laws implemented to enforce EU directives.
Since GDPR compliance is enforced by EU members, many small companies are exposed to (have customers in) most or all EU jurisdictions, and the EU is very heterogeneous when it comes to regulatory enforcement by member states, I think that they're correct to be worried about the ambiguity around the GDPR.
I'm not arguing against the GDPR - I'm in favor of data protection - but the if/ands/and buts (e.g., speculation) about who is going to get fined, and for how much, is uncomfortable.