Scanners are rated with optical resolution, which is the actual resolution of the scanner, and with their digitally enhanced resolution. Optical resolution should be the measure of the machine when comparing prices not the digitally enhanced resolution, which is called interpolated resolution. Interpolated resolution is where the image is enhanced by the software that comes with the scanner. The image is enhanced with a software algorithm. Images appear as if scanned at a higher resolution.
Interpolated resolutions are often significantly higher than optical resolutions.
Both the optical and the interpolated resolutions are given in dots per inch or dpi. You need to find out if the 2400 dpi resolution shown on the box is optical or interpolated before comparing prices. Another comparative feature is the number of bits supported by a scanner. The more bits the more image can be handled and processed. The scanners with the highest bits are generally of the best quality, all other things being equal.