Well I just completed one of the regular marks, and many of these are not even NMs but monsters that have been around- Adamatoise, for example. Killing 4 of them netted me 1 note.

The other 4 marks all reward 1-2 notes.

So that's like 5-10 a day depending on your luck in which marks you get for the day. There is only one elite mark a week and from the looks of it, it's only 20 notes. One weapon costs 1740, and every piece of gear costs 600 or 1000 each. It would take a very long time!