When you pay more for an eyepiece you are usually paying for: Field of view: Eyepieces that have many lenses to correct for the five major aberration (these aberrations give increasingly worse, the lower the focal ratio of the telescope) have obviously higher costs in lenses and coatings. Eye relief: Using larger, more expensive elements in eyepieces allows for a greater distance between the eyes and eyepiece. Coatings: 2-layer multicoatings on both faces of all lenses will typically add 25% to the cost of an eyepiece, but this is absolutely necessary to preserve the contrast of the image when the light has to go through 7-9 lenses. Advertising: Those ads aren't free.