Stopped reading after two pages:

Real Life:
Mail:
Postage costs $.50 to send a letter. That $.50 goes to the Post Office to cover their costs for processing and delivering that letter. They now have $.50 more in their bank account to spend on something else and this is repeated over and over again.

FF14: (saying 50g to keep the numbers the same)
Postage costs 50g to send a letter. That 50g goes poof and is never seen from again. The Mail Moogle does not have your 50g - it has left the game forever.

Before sending the letter in game there was 1 million gil actively available in the game. After sending it there is now 999,999.50 gil in the game. Everything involving spending Gil in this game causes Gil to be removed from the game permanently.

Personal Wealth is irrelevant.