Tile installation with additional costs for large format

Dear forum members,
I have been in a construction phase for two years. Now finally tiling is being done. The developer has charged me an additional cost for large format tiles of €7,977.00 in this regard. It concerns the floor tiling of 94sqm. The tile size is 120x20. The additional cost is listed in the invoice as follows:
1. Additional material tiles extra cost €2,707.00
2. Additional cost laying €1,770.00
3. Additional cost large format €3,500.00.
My question: Is this additional cost justified? I would be very grateful for helpful hints.
Kind regards
Th. Tiede

Good morning. We also build with a property developer. Based on my experience, it could be due to the following reasons:
A budget for tiles is specified in the construction and service description, if tiles are planned at all. You are obviously deviating upwards in price there (point 1).
For us, only tiling in the bathrooms is included in the price. We have to pay extra for the hallway and kitchen. That could explain point 2 for you.
Deviations from the standard format downwards and upwards can probably be more complex when laying, e.g. it takes longer or you need 2 people. That would be point 3.
Without knowledge of your construction and service description, this is just a guess. However, your property developer should actually be able to explain this to you exactly. However, I cannot say whether the prices are reasonable.

120x20 or 120x120? We are currently laying tiles ourselves and our construction specifications state that for tiles larger than 30x60 and calibrated tiles, significant additional costs arise due to extra effort. Therefore, we agreed everything beforehand. In the end, we stayed within our "budget" because we tiled fewer walls than stated in the construction specifications.

Laying of large formats and special sizes is additional work and therefore surcharges are charged. One tiler charges more, another less. One general contractor charges more, another less.

1. Additional material tiles extra cost €2707.00

2. Additional extra cost for laying €1770.00

3. Additional extra cost large format €3500.00.

More waste
More effort
Difficult handling, longer execution

Hello, I am only a DIYer, but I have at least already laid half the house with 120x20. The waste also results from the laying pattern. If, for example, a random bond was laid, then the waste is very low. There will probably always be a second person involved who prepares the tiles (buttering-floating method) and hands them over - increased personnel effort. Presumably, a leveling system will also be used because such tiles often have a slight "dish" shape. Furthermore, it could be that, for example, an S1 adhesive was used instead of a normal flexible adhesive.

Overall, I would not have expected such additional costs to arise. The material costs alone of 2707 euros. Nice wood-look tiles in that format cost about 30-40 euros per sqm. If you now assume 5 euros per sqm for the additional price of the S1 adhesive, then the tiler would have had 60 sqm of waste... The second position of 1770 sounds realistic. But then what is the third position supposed to be?

...
But what is supposed to be the third position then?

Probably no tiles are planned for this area in the construction and specifications? Then there is an additional charge, which should actually be offset against the other floor laying method. At least that’s how our builder does it. The other surcharge is then for the tile size as you explained. But only the OP can tell us what is stated in the construction and specifications!