Why is _no one allowed_ to install my washbasins?

Is this way of thinking wrong?

Correct, but already discussed here. The general contractor or his subcontractor is supposed to take a part supplied by you on consignment, meaning 1. to bear the risk that they cause a stress hairline crack during installation (or even completely break it), and 2. to bear that in case of warranty claims, manufacturing and installation defects are difficult to distinguish, and on the one hand they bear this risk but on the other hand end up empty-handed regarding the commercial margin?

Just ask. But it is extremely rare that you will find a plumber for that. And bring up the topic of warranty.

Just ask. But it is extremely rare that you'll find a plumber for that. And bring up the topic of warranty.

yes I understand that, no question! I also think that of course there is no general contractor who just says: no problem, we'll do it if you want!

The question is only to what extent he might still be willing to compromise and really wants the project.

From what I read here, it has worked with one or the other before!

We'll just give it a try, talk openly about the pharmacist prices - maybe then we can negotiate in other areas and make up the savings potential elsewhere. Ultimately, it's all about negotiating.

exactly right! Wherever you see that the price of the Sanis is no longer in any relation to the one on the internet, you should address the GU. For me, it was about a stupid HTHK that was simply supposed to cost double and the installation is actually a breeze. This industry is simply a cartel or a mafia

If the main contractor calculates a €500 washbasin and credits you €200 for removing it, they have also made their margin.

that's exactly right!
Where you see that the price of the sanitary ware no longer stands in any proportion to that on the Internet, you should address the general contractor.
In my case, it was about a stupid HTHK that was supposed to cost twice as much, and the installation is actually a piece of cake.
This industry is simply a cartel or a mafia

I see it exactly the same way. I was so shocked when we had an appointment recently and went through the prices for the standard equipment.
Afterwards, I browsed the Internet and saw potential savings of about 40-50% on average for the IDENTICAL products...

That is really by no means in any proportion!