What is the appeal of the Denon 103 cartridges?

@billwojo If you were paying attention, I'm replying (and quoting) directly to the OP.

Different religions assume different beliefs. The same apply for
this question. The English saying is: ''I am not rich to buy cheap
stuff''. The other say: ''no better deal than bargain''. 

I think the 103 is a great cartridge.
I currently have 2 on a 2 armed Artisan Fidelity Lenco.
one is stock except for a Nasotec aluminum body. The body cuts down on extraneous resonance and most importantly makes mounting much easier (no nuts required). This cartridge is mounted on a Fidelity Research FR64S, which I have found to be the perfect arm for the very stiff Denon.
 The other is a fully kitted SoundSmith “Gold” , which has a wood body, brass top plate, ruby cantilever optimized line contact stylus.
 The suspension has also been modified to be higher compliance.
 It is mounted on a Analog Instruments Seggwan arm. This is a 12”cocobolo unipivot.
both are feeding SUTs: one is a Ypsilon MC16, the other is a DIY 15x Shure transformers. I swap SUTs and phono preamps from time to time.
cut to the chase:
i prefer the stock one.
 The stock lacks the detail of the Gold but it makes up in body and richness. I have found that correct azimuth makes as much difference with the spherical as it does with the LC. Once you achieve perfect phase angle the details are quite excellent and the body is superior.
 I still like the hot rod gold; on Ac cappella choral music it has a immediacy that is quite seductive. Smaller group pieces such as string quartets and lieder are sublime. 

consistent build - very good left right channel balance
good sound as standard - there's nothing offensive about it
good value
re-tipping transforms them
you don't have a heart-attack if you do damage it
you just don't obsess and simply listen instead of waiting for high end fireworks

The stock Denon is not calibrated for perfect channel balance, for this reason Zu Audio calibrate them to select and sell the best samples with perfect balance.

Re-tipping make no sense, because a brand new cartridge cost less than re-tip alone. 

At higher price better vintage MC cartridges available with better styli and better cantilevers, as a result much better sound. Investment in Denon make no sense for this reason, refurbishing make no sense too. Some people just love to mess around with them, in the end the overall price is way over some other nice MC cartridges that does not require any mods at all.