The lens is probably more important to image quality than the operation of the camera. You could have a high megapixel camera and great performance however if the lens is not sharp, the image will not be sharp. Professional lenses from the most common DSLR manufacturers will vary greatly but for a quality lens you will be looking in the $1000 to $2000 range and from manufacturers like Leica they can be as high as $5000. What is the difference in a lens of this quality over that of a “kit lens (one that is included with the camera)” is typically the speed (or aperture) and the sharpness. A fast lens has a low aperture rating such at 2.8 or lower. These “professional” or Fast lenses typically are ground to very fine and strict guidelines and are typically coated to provide a very pure image to the sensor.
If you want to take great photos study composition if you want to have sharp images invest in a quality lens.