@abfab
As you said, once the concrete is dry its too late. We were asked by the electrician if we wanted some special stuff, spotlights in some places for decor, etc. To keep the cost under control, we rejected all the "extra" stuff, e.g. - 3 sunken spotlights in a cubby hole in the living room to keep some decorative stuff. We also rejected electric blinds coz they were expensive. Should've seen your post earlier.
For us it was CHF 180 for each extra socket and 5K for the kitchen granite (the wife absolutely wanted granite... nothing else can do). Still bracing for the sanitary ware offer. Surely it will be another dent in the budget.
But its fun...