I can see this being something to do every once in a while. But the overhead to get that many maps for the guild would be overbearing. And to get everyone in the guild to level a gathering class to get a map to just give all the profits to the bank also is not something that is very feasible. No other reason to level gathering... everything you get sells for 1-15gil more or less.

I done the math as well and it would slowly get you gil. But the rate is just horrid. 7.5million with 80 people. Lets break out the math of exactly what that is.

560 hours of work (1hr for all 8 per day x 10 partys x 7 days) + about 13 hours to farm all the maps as a collective (10mins x 80 people). So 573hrs per 7.5 million = 13,089 Per person per hour. That is just not an acceptable amount of gil... almost anything else you would do would be more then that. Running a dungeon with philo gets you like 10k in mob kills and a 7k philo item at the end of an hour.

Now you get more then gil yes... but the markets are garbage on all servers so most mat drops are 1-100gil each even if hq. And even if you sell the shards and rare philo mat drops you will be pressed to break 17k/hr gil per person average.

And the fun part getting people to give up "THEIR" gil to the bank at the end.

To any guild that can pull it off for the long term my hats off to you. For me this only works on paper not in practice, the low rewards and way it is collected will not work over the longterm.