Cold water faucet + drainage connection for washing machine

That already looks very advanced with you... I thought you were still in the planning stage...

If all the walls and ceilings are already up, this will be an expensive pleasure...

(You should ask more precise questions. You ask what the connection, sink, base cabinet etc. costs. Later you say you want to do almost everything yourself. Now we learn that the child has already fallen into the well)

I'm out...

Yes, that will not be cheap unless you arrange it directly with the plumber, then he might do it for a low three-digit amount. A sink connection and a washing machine connection are completely different services.

I never asked anywhere about the cost of a washbasin or the cabinet underneath. Ok, one could understand it that way. All cabinets go through me. It was only about the technical implementation. That a hot water connection/angle valve is available and instead of a standard cold water tap for the washing machine also an angle valve. The drain would already be there because of the washing machine, where – I think – nothing else needs to be changed.

For this, the plumber is now giving me a quote of 300€ gross including siphon and an inlet pipe (for whatever reason?). However, it was already installed/attached last week. The plumber is finished with his pipe installation. So visually, what the kitchen picture shows.

Then just request the service, tell the plumber it costs 300 €.

And then the unanimous opinion will be:
Yes.
Before execution it would have been half, afterward 300 is completely fine.

Well, then the child is already in the well.

I think you don't understand me right now, or we are talking past each other. In the initial meeting, I addressed the general contractor for plumbing about this request. There was no offer, even after asking twice. He built it last week. But now he is sending me an offer for something he has already completed. In my understanding, the offer is given before execution to be able to clarify questions regarding the offer and to agree to the execution. Clearer now?