No, the way GDPR is written, the cost is null for most small startups in europe. And for the startups in need of personnal data, either the ammount of data that need protection is small (like a birth day field) and will need at most ~4 day (counting deployment) to be corrected, or they are working with state-related business (at least in France).

Source: i'm currently paid to create ML and data analytic clusters for startups and to give some advices on regulation.