5. Where making high-value datasets available free of charge by public sector bodies that are required to generate revenue to cover a substantial part of their costs relating to the performance of their public tasks would lead to a substantial impact on the budget of the bodies involved, Member States may exempt those bodies from the requirement to make those high-value datasets available free of charge for a period of no more than two years following the entry into force of the relevant implementing act adopted in accordance with paragraph 1.