Some examples of how much TC it's possible to get by submitting a good item:

If you made an item as cool as Daimyo Hat & Scarf hairstyle, you'd be able to get more than 1.25 kk in the long run.
Surfer's Seishin would have generated 400k+ for its forger by now, Centurion - 700k+.
If Cyborg full set was user-created, it would give its creator 100k per each purchase and it would have made 700k in total now after a few months.