- The main difference between a custom hearing aid and the MD Hearing Aid AIR is that a custom hearing aid is programmed specifically to the patient's hearing loss. This requires a number of visits to the audiologist or doctor and also has an extraordinary cost associated with it, between $1,000 and $3,000 for a custom programmed hearing aid. br br The MD Hearing Aid AIR offers a lot of the same components, performance, quality of sound at a fraction of that cost.