Hope it's alright to ask this. I'm not actually a tiler yet but hoping to get into the trade soon. Can someone explain to me why the differences in prices, I.e 30 per m2 for ceramic but 40 per m2 for natural stone or marble etc? And say 30 m2 for 10mm thick (example thickness) but 35 m2 over 10mm thick? Do these m2 prices include adhesive and grout etc?