tall, high, expensive
高 centers on vertical extent or degree: something tall, high in position or level, and by extension expensive (high in price).
high; tall
quantity; amount; volume; number; amount of money
best; supreme; wonderful; finest
senior high school; high school
high-speed; rapid; express
senior high school student
high-class; high-grade; high-quality; high-end; luxury
advanced age; old age
altitude; height; elevation
girls' high school
to rise; to swell; to be promoted
high class; high grade
large sum (of money); large amount
highly priced; expensive; valuable; costly
to raise; to lift; to boost; to enhance
elevation; height above sea level
high efficiency; high performance
high mountain; alpine mountain
high price
rise; swell; elevation; upsurge
high-rise (building); multistory; multistoried; tall
Supreme Court
high temperature
sharp rise (in prices); steep rise; substantial increase; soaring
高 is a pictograph of a tall watchtower or raised structure, with the modern form preserving a roof-like top and a base. The idea of height extends naturally to high cost.
Picture a tall watchtower: the top 亠 is the roof, the middle 口 is a window, and the bottom 冂 with another 口 inside is the enclosed base. The whole structure stands high above the ground.
For コウ, imagine a tall tower so high it touches the clouds, and a person named Kou standing on top shouting 'Kou!' to be heard from such a height.