Within the classes, I'm thinking of breaking down the spoils by quartiles. The top quartile gets 50% of the income; the next 25%; the next 15% and the bottom the remaining 10%.
So taking the cavalry class 42158gp/month (averaging 703gp/month), that actually breaks down as the richest 15 (likely the timoukoi) take 21079gp/month (averaging 1405gp/month); the next richest 15 take 10540gp/month (averaging 703gp/month); the next richest 15 take 6324gp/month (averaging 421gp/month) and the poorest 15 take 4215gp/month (averaging 281gp/month).
For the hoplite class 34585gp/month (averaging 144gp/month); the top 60 take 17293gp/month (averaging 288gp/month); the next 60 take 8646gp/month (averaging 144gp/month); the next 60 take 5188gp/month (averaging 86gp/month) and the bottom 60 take 3458gp/month (averaging 58gp/month).
For the artisan class taking 27012gp/month (averaging 90gp/month); the top 75 take 13506gp/month (averaging 180gp/month); the next 75 take 6753gp/month (averaging 90gp/month); the next 75 take 4052gp/month (averaging 54gp/month); and the poorest take 2701gp/month (averaging 36gp/month).
Interestingly, the poorest of the cavalry class earn less than the richest of the hoplite class, and there's an even broader overlap between the poorest three quartiles of the hoplite class and the richest two of the artisan class, which sounds about right to me.
Festivals - of which there are potentially many in the Greek calendar cost 6000gp, and as mentioned are voted to a citizen to fund as a liturgy, or public service to the city. Obviously there's a great deal of political potential around them - some are prestigious and can make a man's name for the year, but equally they could be used to ruin someone in precarious financial circumstances.
Looking at Demand Modifiers, the factors on that table are relatively straightforward:
Age: 101-1000 years (Massalia is 300 years old at this point)
Water Source: Sea coast (obvious one!)
Climate: Scrub (after some research, apparently most Mediterranean climes are classified as Maquis shrubland)
Elevation: Hills (lots of hilly ground from the tail of the Alps and situated on promontories)
I don't think I want to start with random modifiers for goods-types, but I am confused as to how I apply the reality. The complication is the Massalia was an exchange-point rather than destination for much of it's trade. Its population wasn't that big, things going there weren't for local consumption, but often shipping off again - either to the Gallic interior or out into the wider Mediterranean.
As mentioned before, they exported their own products; local wine, salted pork and fish, aromatic and medicinal plants, coral and cork, salt, olive oil, cups, mixing bowls, to inland markets in Gallia. They were a destination for re-export primarily of grain, amber, tin and slaves.
So perhaps I should read that as negative demand for the first list (since they are produced locally or imported for shipping into Gallia), but positive for the second (since they are things in demand at Massalia to be shipped off elsewhere)? Point then is that if you have the former you need to take them inland yourself, but if you have the latter there'll be someone glad to take it off your hands.
Maybe what I should do is determine the obvious ones, but do the others randomly?
Given the number of settlements Massalia connects to, is this going to get messy when I look at trade routes? The major place it links to is Emporion, which is smaller, and a source of metals.