Electric billing - based on which principle?

I do think that the calculation method is not correct. As already mentioned, a single socket is more expensive because a cable has to be laid, which has to be connected to a fuse. For a multiple socket, only the effort for one flush-mounted box + frame + cover applies.

I do think the calculation method is not correct. As already mentioned, a single socket is more expensive because a cable has to be installed, which must be connected to a fuse. With a multiple socket, only the effort for a flush-mounted box + frame + cover applies.

Ever heard of flat-rate calculation? It’s certainly used somewhere in "your" company too, because otherwise you wouldn’t get a salary. If I give my customers a CD, it doesn’t cost just one euro, but 59€, or this CD is already included in a contract price of 199€. Nobody can come to me with "it’s just a push of a button."

Come on, people. The craftsmen have nothing to give away. Why should a craftsman always charge the cheapest and best for the customer? The customer is more like a "mayfly."

There was a contract, he provides the service. The customer wants something more, so it gets more expensive.

Also, upgrading a car is always more expensive.

The electrician conjures up a "calculation method" here afterwards that the OP could not have calculated beforehand. To be honest, I am surprised by the reactions here. It may be that the electrician gets away with it, but I do not think that is okay.

The electrician's mixed calculation can already work out simply because he charges €90 or €120 for the boxes. That is not little, known beforehand and therefore completely legitimate. If that is not enough, then he simply has to charge €200. If the OP only takes the basic equipment of the house, the electrician's mixed calculation no longer works.

Every change generates logistical and bureaucratic effort. Hardly any client sees this. However, the costs are real. Therefore, changes are more expensive than the pure additional material and labor costs. "Erläuterungsresistente Pfennigfuchser" without commercial understanding are exhausting.

As already said, a single socket is more expensive because a cable has to be laid, which must be connected to a circuit breaker

Does your construction service description even allow for that? It is rather unusual that every socket is individually protected. This is done in the kitchen with separate lines for the stove, microwave, refrigerator, etc., or for the washing machine and dryer, but not in the children's/bedroom/study.

In this respect, the additional effort is primarily a question of the design of "4 sockets per room." If you can get one socket in each corner of the room as standard, the surcharge to make it a double or triple socket should really be limited. However, if the (clever) electrician interprets this as "4 sockets under the light switch," quite a few meters of cable and chases are added, which would then also justify a certain surcharge.

You should clarify that!