No offence to you personally, Flavio, but the fact that you work for Earphone Solutions -- a company that has a clear interest in selling this new expensive product -- makes your post somewhat awkward.
The huge margin you refer to very likely has
a lot to do with the TF10, whose detachable cable is known to be of substandard quality and nothing like the Westone (ES) detachable cable. Also, the TF10 connector is known to be of similar quality, ie not very good or as you call it "a weak link". You yourself admitted there's not enough data to talk about the recent UM2 & UM3X with detachable cables. If what you said were true, why is it that the
vast majority, ie not all, of custom IEMs come with the detachable cables? That has been the industry standard for many years now.
Apart from the TF10 substandard cable & connector quality, there's no reports that I know of of the new UM2, UM3X (and Sennheiser IE8) issues with their detachable cables. Also, although a couple of people don't like the UM2/ UM3X memory wire, I find it very useful both on my ES3X & UM3X, and the memory wire is also used in pretty much
all custom IEMs. In addition, the Westone ES cables can be had in different lengths - I personally prefer the longer 64" cable as opposed to the 50" standard length. Ultimate Ears sell 2 different lengths, too, 48" & 64". Although I don't believe in cables making a difference in SQ -- I think it's pretty much snake oil --, for those who do, they have the option of getting one of those expensive aftermarket cables.
On the subject of durability, I don't doubt you have had your UM2s for 5 years. Unfortunately, that is not always the case and there are many reports of people having cable issues after, or within, the 1 or 2-year warranty period. The fact is that not everyone treats their IEMs equally.
On a related note, both UM2 & UM3X with detachable cables come with quite a few more accessories than the UM2 & UM3X with fixed cables - you get 6 more different eartips, a 1/4" headphone adaptor, and an inline volume control: