Installation prices
Many factors affect the price of installation. Basically time equals money. If an installation is more difficult and therefore requires more days to complete, it stands to reason it should cost more.
But also different materials install differently, as do different sizes of material, as do room layout and tile layout.
Larger tiles are not easier to install but harder. They take longer to handle and are heavier and more cumbersome to mark and cut. Trying to have them overcome the variations in the concrete is more difficult than a smaller tile following the variations. Any thinking installer will not charge the same across the board, but consider all these factors.