some people have a hard time understanding economics it seems...
Say, you have a server with total gil of 600M and 10 kraken clubs as the only product on the market, no shellbuster, no other weapons, no armor, no crafting material, no food, nothing else.
Each kraken club in this scenario is worth 60M because any more than 60M there won't be enough money on the whole server to buy all the kraken clubs.
You put up your kraken club for auction and it sold for 60M. Total gil on the server is still 600M, even though you personally just gained 60M. Still 600M on the server for 10 clubs, so each clubs are still worth 60M, no inflation.
Now you go farm spark and accolade, you made 60M from buying shield with spark and sell shield to NPC for gil. Total gil on the server is now 660M and you have personally gained 60M. Now there are 660M gil on the server for still 10 clubs, so each clubs are now worth 66M, there is inflation.
It may feels the same to you as in both scenario, you've personally gained 60M, but to the server, only in the 2nd scenario does the money supply increase.