I'd agree that modded units appeal to a much smaller group of buyers than stock equipment, and are therefore somewhat harder to re-sell. I can think of 4 factors that are relevant:
First, the mod invalidates the manufacturer's warranty (although the firm doing the mod may offer a warranty).
Second, all mods reflect, to a greater or lesser extent, the audio quality deemed "desirable" by the person doing the mod. This makes the mod a much more subjective process than sticking with a stock unit that sounds the same for the entire model line.
Third, some mods simply sound different, and not necessarily better, than the original unit.
Last is the question of whether the incremental improvement gained from a mod is worth the cost (which can often be quite high), or whether it simply makes sense to spend more money initially and get a much better piece of gear that is manufactured in large enough quantities to benefit from the cost savings of production runs.
First, the mod invalidates the manufacturer's warranty (although the firm doing the mod may offer a warranty).
Second, all mods reflect, to a greater or lesser extent, the audio quality deemed "desirable" by the person doing the mod. This makes the mod a much more subjective process than sticking with a stock unit that sounds the same for the entire model line.
Third, some mods simply sound different, and not necessarily better, than the original unit.
Last is the question of whether the incremental improvement gained from a mod is worth the cost (which can often be quite high), or whether it simply makes sense to spend more money initially and get a much better piece of gear that is manufactured in large enough quantities to benefit from the cost savings of production runs.