Wood-look tiles grouted with the wrong color - redo completely?

Because you can only withhold everything if the defect excludes usability.

In fact, you can of course withhold "too much" if there is no way to get at least a reasonably good response otherwise. The discussion is then based on the work not performed as agreed (facts) and the payment not made as per contract (facts). This only works if the amount withheld causes sufficient dissatisfaction with the situation on the other side. Therefore, it is better to withhold a little more than you aim for as a negotiation target. The reason for this trouble is provided by the service provider, after all. What comes out in the end is another matter.

We have agreed with the developer:

The niche in the shower will not be charged and we will be credited with 750€.

For me, tone on tone would be absolutely nothing either. But 300€ for a shower niche really sounds cheap.

I have no comparison, but I didn't find it a small amount of money.