It's worth noting that home ownership could actually be a rarity in Eorzea, and that would explain why the lowest-end houses start at roughly 3 million gil. Then again, housing prices make absolutely no sense when you consider there is no upkeep cost - when, in a separate reality, owners of those properties would definitely be paying property taxes at the very least. Speaking of taxes, I wouldn't be surprised if that was a significant proportion of the money that goes into the coffers of each city-state's respective government.
Also worth noting that billionaires do exist. I remember during the final Beast Tribe quest that the villain spent some billions (it might actually have been trillions - it's been awhile) of gil on his crazy little contraption, so while even us adventurers are most definitely upper-class citizens with our many millions, there are still NPCs with such wealth that they are untouchable for anyone save the absolute wealthiest of PCs (though I don't think there's a single player who has 1 billion gil in existence yet... or rather, maybe I just haven't heard of it).
I don't think using NPC-vendored food works for judging value, either, considering that in an actual reality that food would most definitely be dealing with supply shortages that video games with infinite quantities do not deal in. This is especially true when you consider that Eorzea is still not a heavily industrialized area, and modern agriculture is not yet a thing there (though they do, at least, possess some level of mechanization). If anything, I would expect that any given food item in Eorzea should actually be more expensive than their equivalents on Earth. We have huge quantities of food here relative to what we had in past eras, and TONS of it goes to waste. Eorzea likely deals with food in a very different fashion.
All this to say that, really, trying to deal in hard numbers here is likely to only add to your confusion. At the end of the day, it IS a video game, and lots of abstractions have to be made for gameplay concessions over lore. A bit of a shame if you really like the virtual world aspect of the genre, but it is something we just have to deal with.
Also worth noting that billionaires do exist. I remember during the final Beast Tribe quest that the villain spent some billions (it might actually have been trillions - it's been awhile) of gil on his crazy little contraption, so while even us adventurers are most definitely upper-class citizens with our many millions, there are still NPCs with such wealth that they are untouchable for anyone save the absolute wealthiest of PCs (though I don't think there's a single player who has 1 billion gil in existence yet... or rather, maybe I just haven't heard of it).
I don't think using NPC-vendored food works for judging value, either, considering that in an actual reality that food would most definitely be dealing with supply shortages that video games with infinite quantities do not deal in. This is especially true when you consider that Eorzea is still not a heavily industrialized area, and modern agriculture is not yet a thing there (though they do, at least, possess some level of mechanization). If anything, I would expect that any given food item in Eorzea should actually be more expensive than their equivalents on Earth. We have huge quantities of food here relative to what we had in past eras, and TONS of it goes to waste. Eorzea likely deals with food in a very different fashion.
All this to say that, really, trying to deal in hard numbers here is likely to only add to your confusion. At the end of the day, it IS a video game, and lots of abstractions have to be made for gameplay concessions over lore. A bit of a shame if you really like the virtual world aspect of the genre, but it is something we just have to deal with.