Really watch out for the prices of earthworks. If the plot has a slight slope, the excavation will be significantly more. Depending on the soil condition, the excavation can then be used again for backfilling or not. If not, filling material must be purchased (gravel, humus...).
The distance to the nearest landfill is also important. Some earthmoving companies are so bold as to sometimes charge a flat rate instead of individual billing in cubic meters. And some calculations are made such that the company plans to store the excavation on the property or at the neighbor's. When the excavator then arrives, the construction company suddenly realizes that it actually has to be transported away because there is not enough space or the neighbor simply does not want anything stored on their (empty) property.