it's the qty they have that I want to know...
I take in a lot of raw new players with baby cities into my FS so I do a lot more teaching and guidance. This helps widen the net we cast with recruiting as they don't need to be Spire capable already when they join, but can develop into one. We have a sustainability spreadsheet as training wheels to help players get themselves able to climb the Spire independently and sustainably. It's completely optional to participate. You list your inventory on Tuesdays before start of tourney (more variable and open ended, potentially costing more than the week's Spire). Ideally, they want their inventory to be growing a little overall each month to build up what I call their "war chest". If there are too many consecutive rows of red, then they know which tier of goods they're crashing on and perhaps need to build more of that factories.
Only about 25% of the FS choose to use it. Of the 25%, I would say half of them are already sustainable and don't even need it. Some start with it and ween themselves off when they get the hang of it. Curiously, some of the players with the biggest banks continue to use it, even though they've already grown their inventory to the millions. A few times, the mages were able to spot a trend before the player did to help them course correct by advising more factories. We'll happily throw goods their way if they want it to help soften the upgrade adjustment period if their factories are out of production. Other times, the crash might be because they took a really high level wonder out of rune stage (thanks to rune blitz, some people have lvl 30 wonders before they're out of chapter 5) so it's not a sustainability concern. I also have a Sustainability Mage who, like
@iamthouth, are Elvenarchitect pros that doesn't mind taking the time to help you 1-on-1 to find fat to trim and more efficient layouts. However, we had one guy whose numbers crashed when he got to Dwarf. When we alerted him that he would have a hard time treading water if he continues to tech at the speed he was advancing, he got too overwhelmed and retired. To his credit, his very first FS ever was a gold FS and he had been able to summit the Spire since chap 3 all the way to Dwarf. All he had to do really was take a breather on the tech tree to regroup and he woulda been fine, but I guess real life fires + elf game fire proved too much.
"What do you mean you won't do a 1:8 trade? You have millions of planks, you jerk!"
Because everyone knows the spreadsheet exists regardless if they use it, they know the goal is to get themselves independently sustainable. We give ample help for those who wants it, but they also know we're not here to give endless handouts if they're making no efforts towards sustainability. Having a sustainability program is a good deterrent of the beggar mentality. We're here to empower you into mighty little cities!