It varies a lot. You can expect anything from a few hundred to even a few thousand EUR in costs. It depends on the service provider and the complexity of making these amendments (for example, how many shareholders there are).
But if we assume it's a single shareholder/director company and you're using some average corporate service provider (not the cheapest, and not an expensive law firm), I would suspect the cost to be in the range of 500 - 1000 EUR.