Electrical installation in a prefab house seems very expensive to us?!

Looks similar with us as with you - about €20K for 165m². Regarding the points you mentioned here, also the electrical box with 4 meter slots, separate sub-distribution for the upper floor, installation including Warema control. When I think about how long the guys were wiring there... The price is fair!

What do you plan to do with four points?

We are preparing for all eventualities... regular electricity meter (of course), heat pump (IN CASE it ever becomes worthwhile... probably not), photovoltaics (so far only in preparation, but will probably still be installed), electric vehicle. I also thought it was crazy, but according to several opinions (also here in the forum) not that far-fetched. But if you had all of that, of course you would have 4 x basic fees. We'll see where this goes, the box wasn't much more expensive anyway. Retrofitting is definitely more annoying.

I have also planned a separate sub-distribution board for each floor, plus one in the garage, which separates my garden/outdoor lighting as well as photovoltaic/electric car from the rest.

I think it is worth planning more comprehensively here.

So we are looking at a new build, 177 sqm with everything included, including preparation for photovoltaics, a generous number of sockets, satellite dish, power cables, distribution box, LED lights in the kitchen and bathroom ceiling and on the stairs, plus electric shutters with central control and many more, at €16,000 gross. I would definitely get another offer. For the equipment, I find €18,500 way too expensive.

I would always insist on receiving a complete offer that clearly shows how the final price is composed. The same applies to the billing: How many meters of cable/conduit were installed? How much working time? etc. This way, offers can be reasonably compared.

With this flat-rate rubbish, as a client, you ALWAYS fare worse. You can certainly count on 15%-20% safety margin that the electrician includes and that is ultimately added on.