You said the same thing in
another thread, but I never got a response after disclaiming it.
Oh... i never seen your comment... I am not sure however, what's there to disclaim. My comment was/is, that Corp Maintenance is growing with city size, which is true. No valuation/opinion there.
As to valuation...
EDIT: [...]
The whole point of spreading those Corporations is to grow the city, so if growing the city wasn't profitable (or deemed "worth it") to start with, then you'd think the Corporation would've never been spread there in the first place.
Now, that's exactly waht i am talking about.
There are cities (games/empires/situations/...) worth spreading Sushi into them, and there are others, where growing is not worth the trouble/expense. Spread into the right cities, and you are fine. Brainless Sushi Spam can harm you.
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Assuming the Number of Ressources beeing constant, sure, if it's profitable to plant Sushi there in the first place, then no harm is done in the city actually growing...
How about aquiring new ressources and growing even bigger ?
Another thing is - not only the Maintenance for Sushi increases with size. Having another Corp in the same city, will have it's fees increased as well, without the benefit changing...
Let Look at a Example. A mature, well developed city in reasonable good land.
The Corporations Costs are:
(4 + #Ressources_used) * (City_Size + 17)/18 * 0.5 - 12
* 0.5 is from Courthose, 12 is the

from the Headquaters under Wall Street (it's not in the city in question, we just assume it does exist somewherwe), which we substract from the fee.
Assume the city at it's full natural size of 20 in food equilibrium and working all plots.
Also the City has Mininc Inc already, before we Plant Sushi. Mining+Sushi is a favoured combo i recon...
Mining has 16 Ressources giving us 16

:
20 * (20+17)/18 * 0.5 - 12 = 8.56

for 16

. Hard to beat that.
Now plant sushi in it with 20 ressuorces:
24 * (20+17)/18 * 0.5 - 12 = 12.67

Initial Maintenance.
Now using the newly aquired 10

for 5 additional Pop the city grows. Since Mining does not benefit from additional Pop, but becomes more expensive, we add those additional cost to Sushis fees as well:
24 * (25+17)/18 * 0.5 - 12 = 16

20 * (25+17)/18 * 0.5 - 12 = 11.33

- 8.56
Where do we stand now?
18.77

we are Paying for 5 Specialists.
We would have to run 3 merchants under 100% multipliers to offset 18

fee.
So the net gain of Sushi in this city are 2 free specialists. Still not bad.
So much for the preliminaries. Another Question is:
Is it worth now to trade for more Sushi ressources, to increase the bonus ?
Assume we aquire 4 more Sushi-ressources for 2

to grow the city one more point....
28 * (26+17)/18 * 0.5 - 12 = 21.44
20 * (26+17)/18 * 0.5 - 12 = 11.89
6

more Maintenace for one more specialist... So if we run him as Merchant we are roughly breaking even. We did however went into some trouble to aquire 4 more Sushi ressources (Giving Ressources to AI, or Planting a City to grab more Fish...)
Another one ?
32 * (27+17)/18 * 0.5 - 12 = 27.11
20 * (27+17)/18 * 0.5 - 12 = 12.44

This one comes at 6.22
Never seen Sushi giving me more than 14 food, so i stop here.
The point is: Each added Sitizen you gain from Sushi becomes slightly more expensive than the previous one.
Also note all of this is noble. On Monarch there is a additional (* 1.2) so 6.22

becomes 7.64

to pay for one dude.
On the other hand Corps are often run under free market, which would again lower the cost... But this also means, that you don't run - just for example - Mercantilism, which is one Specialist less again...
In the right city and under right civics it's worth it.
Spamming it brainlessly, can make the cost more than the benefit.
Many things play into it, so the question if it is allways worth it to go for Sushi / spam it in every city / max-out it's ressources does not seem that ridiculous to me.