A single 18-200mm is usually priced higher mainly because it offers convenience: one lens covers a very wide range, so you change lenses less often or not at all. That convenience has real value, and designing a lens that works across such a large zoom range is also more complex.

In general, superzooms like 18-200mm are a compromise lens. Compared with shorter-range zooms, they often give up some sharpness, have more distortion, and are relatively slow at the long end. The two-lens option can be cheaper, but those kit lenses are also basic lenses and not necessarily high quality either.

Price differences also come from other factors besides focal length, such as build quality, autofocus motor, and image stabilization.

So the choice depends on priorities:

• Choose 18-200mm if convenience and fewer lens changes matter most.
• Choose 18-55mm + 55-200mm if lower cost matters more and you don't mind swapping lenses.
• If image quality is the main goal, spending more on better lenses with less zoom range—or even primes—often gives better results than either budget kit zooms or a superzoom.