By the way, this is wrong. You need to consider the system as a whole when comparing water cooling vs air cooling.

You need at least N square centimeters of surface area to transfer 250W of heat to the air no matter the cooling solution: whether this surface area is the fins of a heatsink in an air cooling setup, or the radiator helping water exchange its heat with air in a water cooling setup. (And as you pointed out, water cooling in general uses even more surface area to allow using slower and larger fans.) Now what do you think require less material and parts:

(1) have the N square centimeters of metal sitting right on top of a chip, or
(2) have the chip transfer the heat through a water block, to water, through a pump, through a radiator.

Obviously (1), that is air cooling, requires less material and parts, and less assembly overall: the same N square centimeters of surface area is required (or less), but there is no water, no pump, no water block.