Price difference between windows vs. fixed glass element and masonry?

We have planned a floor-to-ceiling double door on the ground floor floor plan (approximately 215 cm high and 150 cm wide, about 3.2 m² glass area, two openable wing doors) and would like to replace this double door or double window with a fixed window in order to implement a seating window inside via a carpenter.

That means the position in the floor plan would remain the same, as well as the width and the top edge. The fixed glass element would then no longer be floor-to-ceiling at the bottom, but would end about 50 cm above (then about 2.5 m²).

I had assumed a price reduction because the window area becomes about 20-25% smaller and all the door mechanisms are omitted. The construction company is now talking about an extra cost of 400 euros net / about 480 euros gross because the 50 cm at the bottom require extra masonry work, an external window sill is needed, and a fixed glass element in one piece is large and heavy.

The window sill makes sense to me of course, but in the scope of services description we do not have very expensive window sills (external window sills made of aluminum including anti-drumming foil with side finishing profiles and drip edges). However, I would not have expected approximately 0.8 m² of additional masonry to be a major cost factor, at least less than the presumed savings from the smaller window.

Does anyone have experience on how this should be assessed in terms of price?

Even if someone calculates this for you, it won't help you. You want it that way and the contractor has given you his price. Either you accept it or you don't. If you come with "But it will be cheaper, I want a discount," he will probably say "Alright then, you'll get the window as stated in the contract at the price already agreed upon"...

The doors are installed by the window installers detaching the sash, setting the frame, and re-hanging the sash. Such a floor-to-ceiling RC2 sash weighs around 100 kg. You can well imagine that for a glass element weighing around 200-300 kg, the effort is significantly higher because something like that can no longer be handled by manpower alone without equipment.

Aside from that, the contractor has planning effort, drawings need to be adjusted, the new element measured and ordered. Do you think the people in the office who handle all this work for air, love, and kind words? If that takes an hour of effort, you’ve already “used up” at least 100 bucks gross.

For us, the fixed elements were cheaper than the casement doors. But our window installer came with equipment anyway, since we have a very large lift-and-slide door. Also, as my predecessor points out, that’s pretty pointless. If you’re lucky, you might be able to coax another hundred out of the general contractor with some good persuasion. Probably not. You’d better use your energy for other things.

I expressed myself poorly, the 400 euros net is the additional cost for about 0.8 m² more wall under the window, the fixed window itself is supposed to cost about 300 euros net more than the floor-to-ceiling casement door. That seems strange to me in combination, so I am trying to find out a reasonable magnitude. The planning is being done by another company, so the construction company has no effort with it. If I cause additional effort, I am happy to pay for it (here it is like with NatureSys, a large lift-and-slide door is planned just one meter from the window in question, the heavier equipment will definitely be needed), but in this case the scope of almost 1,000 euros gross does not really seem consistent.

Maybe. I also didn’t see why I should pay a 200 EUR surcharge for a thermostat from Vigour compared to a single-lever mixer. Or 2,000 EUR extra for a bit of colored plaster that a plasterer slaps onto the base in half a day, material cost for the operation maybe 300 EUR. Consequence? I didn’t take it...

You won’t have another choice either. The contractor has you hooked and can basically name you any price, you don’t have to buy it.

That’s always the problem when you want to change something after signing. You have no negotiating power anymore... if in doubt, the contractor can always say “Fine, then not. We’ll build it as stated in the contract.”

That is completely correct and usual, we have also turned down various things before. I am only interested in an assessment of what is realistic so that I can better consider whether the additional fantasy surcharge is still worth it for me. ;)