For basic safety, a $30 helmet will provide just as much protection as a $300 helmet. Generally speaking, more expensive helmets are lighter, fit better, and (depending on your point of view) are more attractive.

Tamago stocks a solid, basic black urban helmet for $30 which is sufficient for short rides.

Bern offers helmets in the familiar round urban profile. They’re lighter, come in a range of sizes and colors, and are compatible with accessories such as helmet-mounted LED lights and winter liners. ($40-70).

KASK is the premiere performance-oriented helmet line on the market. Even the base models are feather-light and more crucially offer excellent ventilation, which is crucially important for longer rides in hot humid weather. ($100-300)

Bern Helmets 

KASK Helmets