I was thinking, this system would probably lower my incentive to find the remaining codecs for Mythic items.
What if more codecs lowers the cost?
If it costs 25TS to make a Mythic, it should lower to 15TS if you have 10 codex, and 5TS if you have all 15. After that leads for Mythics no longer drop and it is deemed 'Collected'.
Only cost for Mythic at that point is 5TS, Decon = nothing.
That would actually incentivise me to complete all the leads at get 15 codec on all of them.