I've concluded that tiles are sold as a loss leader & the money is made on adhesive & grout.
Large tub of adhesive - enough to cover 8 sq mtrs - did it hell. Ran out at less than 5 sq mtrs - applied with regular notched trowel, not excessively.
Grout was the same. Tub also claimed "enough to cover 8 sq mtrs". & didn't last till 6 sq mtrs.
So you have to go and buy another of each & use about a quarter of a tub, storing the rest in the shed for 10 years in case it "comes in handy".
Paint is the same. Small can not enough, big can far too much - I suspect they know the average room size & package accordingly.