These two posts above combined easily make an explanation for half of the used market, or market altogether, troubles. Add other distractions (computers, phones, etc.) and who is left to buy an amplifier that costs, used, as much as a quarter of an average USA family income? Ok, that may be exaggeration, but prices of new, and consequentially used, equipment are repelling to anybody but die-hards.
The part to emphasize from the posts above is that there may be lots of people (maybe really hundreds of thousands) out there who have decent systems, but have no interest in carrying around new speakers and amplifiers bi-monthly, and probably losing money while doing it. They settle with what they have, sometimes even quite expensive, and live with it for 15 years. They go through 4-5 amplifiers in life and do not feel they have missed much. The crowd that changes things often, chasing some special sound, must be very small. If for no other reason, then because college tuition is going up, it seems like, daily.
The part to emphasize from the posts above is that there may be lots of people (maybe really hundreds of thousands) out there who have decent systems, but have no interest in carrying around new speakers and amplifiers bi-monthly, and probably losing money while doing it. They settle with what they have, sometimes even quite expensive, and live with it for 15 years. They go through 4-5 amplifiers in life and do not feel they have missed much. The crowd that changes things often, chasing some special sound, must be very small. If for no other reason, then because college tuition is going up, it seems like, daily.