Hi Xystic - I am going to have to disagree with some of your post. You are using "Gil in Cirulation" as just the amount that is spent on the MBs. You are not taking into account the money earned through quests and the likes (which I will grant you are small a this time) and money spent on porting/repairs/MB Fees. I believe you are trying to bleed-in "buying power" of the gil along with the "raw transactional gil" changing hands.
To use your example, lets say that 100mm is changing hands each day, we do not know if that is 2 transaction for 50mm or if its 1,000 transactions at 100k. Market implications are significantly different depending on transactional volume. You are right, we as players, do not readily have this information available in an instant, but it is avail through transactional history, its just a pain to gather that type of data in a meaningful fashion. I am sure once they unlock the XML coding we will have people that will try to pull real-time data from the different boards to websites and the likes.
As I have stated above SE has implemented what I call "gil sinks" to effectively pull gil out of the market permanently. I have posted this in several posts, so here they are:
1) if you came over from 1.0 you lost 90% of the gil stored (my tens of millions of gil went to just millions of gil)
2) selling drops from a lvl 50 mob/gathering spot will only get you 10-12 gil at the max. Same with the high end crafting gear (i have yet to see anything crafter made that sells for over 800 gil)
3) Repair costs (till they "fixed/reduced" the rates) were just a way to suck money out of the economy.
4) Teleports! good god the amount of gil it takes to go from Uldah to Gridana or Uldah to Limsa let alone anywhere to Mor Dhona or Coerthas. (but now they have implemented "Reduced Rates" FC "buffs" to try and dull the pain)
5) Housing - Pricing for this is outlandishly expensive to have at least for the moment and that in 3 months 80% of the FCs will have a "small" house. At least we can be thankful that this isn't as bad as I thought it would be (buying the plot, building tha house, and then paying a monthly "rental fees" to keep the house cause that would be just crazy talk)
6) The 5% sales tax put at the end of the transaction to the seller for the "privilege" to sell their wares on the market.
7) the 5% on what I* call "shipping & handling" tax to the buyer because they are buying an item that is being sold in a different city.
Now given the fact that SE is making such a concerted effort to bleed money out of the market we can only assume that we will have market deflation and your "buying-power" of gil will increase. If there is market deflation you will see the "Gil in Circulation" drop but that does not necessarily mean that "the market is struggling"