The primary cost drivers are material composition and valve technology. High-end taps typically use H59/H62 solid brass, which offers superior corrosion resistance compared to cheaper zinc alloys. The ceramic disc cartridge is the heart of the tap; ensure it is rated for at least 500,000 life cycles to prevent leaks. Additionally, the surface treatment (e.g., PVD coating, electroplating) should pass a 24-hour or 48-hour Acid Salt Spray Test (ASS) to guarantee durability in humid bathroom environments.