Why so many JL Audio Fathom subs for sale I wonder

I have a pair of 110s and have had trouble with one.  Second, the high gloss black finish is very finicky!  Shows every touch and cannot be easily polished up.   I run the pair as Master/Satellite, so there's only one source of low frequency information played through both. 

First of all it is a very popular sub. People who try to integrate one sub are frequently frustrated with the results and eventually give up so their subs show up on the used market. People have to understand that one sub just will not do it. Trying to stick with one to save money will not work. You have to get into subs knowing that you are going to need at least two in the end maybe more depending on your system. JL Audio subs are representative of the upper mid fi of the market. There are just a few manufactured subs out there that are significantly superior and they are very expensive. The Gotham is right up there with the best of them.
Anyway, integrating subs correctly is not easy or simple endeavor. If you start getting frustrated try and find someone with some experience to help out. The only reason to use one sub is knowing that you will have to get a second one down the line. In the meanwhile if you can scarf up a used JL Audio sub at a good price go for it.  

They are a high quality, popular subwoofer but adding subwoofers to a system can cause disillusionment.  

Maybe people are hearing about all the capacitor problems in the amplifier. 4k sub should not be having these problems. Mine just went out. Not happy. 

They are quite possibly the most unreliable subs ever made. Every single one dies. Not worth the premium price at all.  I used to be so gung ho about JL as the best subs on the planet and have changed my tune since literally every single one I have ever dealt with had huge issues.  They’re simply a nightmare.   I have had multiple E112 and E110 sub amps go bad and replaced with “new modules that have fixed the problem” only to have them go bad a few months later.  I have many friends with e series and Fathoms due to my constant bombardment of recommendations and JL cheerleading.  I feel horrible for recommending so aggressively because every person has had huge problems.

I highly recommend Paradigm Defiance or the new Martin Logan subs instead. The ARC inside is painfully good and the subs are musical as hell. They’re not pretty though, that’s the only problem.
Also REL is always good for music.