I've come up with a really crude estimate over the size of Kusari's economy.
Basically, I made a KSP to test out TLAGSNET one day. I was logged in it for about 30 minutes and during those 30 minutes (I believe it was around 12:30 UTC - 13:00 UTC on a Thursday), I came across 6 traders, at least one of which was an unlawful.
Now, the science behind this is based on a lot of assumptions and doesn't take into account a lot of other factors, but essentially here's what I came up with.
Average size of a transport: 3600 cargo units
Average monetary value of each unit of cargo: 3500 (as it is in general the average price of ore sold at a POB)
6 traders in 30 minutes means theres around 12 traders per hour. Multiply that by 24 hours, and you get approximately 300 traders (rounded up for simplification) per day passing through Kusari.
So if we assume that there are 300 trade ships, each with 3600 units of cargo, with unit of cargo worth approximately 3500 credits, we get the following:
300*3600*3500 = approximate/crude estimate of Kusari's GDP per day, let's multiply that by 365 days.
300*3600*3500*365, and according to google you get ...
Now, I have no idea what that number is, so to simplify things, I decided to calculate the daily GDP instead and I got the following:
300*3600*3500=3,780,000,000
Or, in other words, 3.78 billion credits per day passes through Kusari.
So if we multiply 3.78*365 we get: 1379.7 Billion Credits, or in other words, approximately 1.4 Trillion Credits.
Therefore, according to these calculations, Kusari's economy is 1.4 trillion credits each year.
But of course, this is really bad science. Firstly, I've left NPC traders out. I'm not sure they actually matter, because I've seen a lot of NPC 5K ships with 100 units of cargo and 30 units of crew, usually carrying some random thing like food, water, oxygen etc. So they probably don't make a huge dent on the economic figures. Or maybe they do, I don't know. There is no way to know.
Secondly, my statistics are specifically for 12:30-13:00 UTC on a thursday, it does not take into account 02:00 UTC on a Wednesday, when the server is probably dead. Obviously, you would not get 6 traders passing through Kusari at that time. Conversely, you may get 15 traders passing through on 18:00 UTC on a Saturday, but there's no way for me to tell.
Thirdly, as mentioned before, I don't have a way of gathering a lot of data. The average ship size in Sirius may not be 3600 units of cargo. The average ore amount may not be worth 3500 credits. And what about regular trading items that you can pick up on any NPC base? I picked ore value arbitrarily. In fact, many of the assumption I picked, are completely arbitrary. This devalues the accuracy of my results.
Lastly, my calculations don't take into account the services based economy. The only services based stuff I can think of are bounties. I can't think of any others. One would assume that the economy of Kusari would experience a big boom if the Reavers were around collecting bounties against the Blood Dragons and Chrysanthemums. Because, you know, they're reavers. But this stuff is hard to calculate.
Lastly, as mentioned before, I have no idea what impact NPC's have on the economy. I mentioned ore hauling and bounties, but those are just the things that players have an impact upon in the economy. We have no idea how much money the NPC ship dealers make from the sale of their ships each day or year, which would be really cool economic statistical data We could make the assumption that random NPC inRP industries (e.g. we don't know the exact amount that Kishiro Technologies, the entire corporation, makes from the total yearly sales of optronics for example). What about other things like the sale and distribution of sci-data, NEMPs/codenames etc. These are not geographically limited to Kusari. Sometimes they are not even inRP sales, so should we even count them?
CONCLUSION:
I think the best my estimate shows is maybe a value of the shipping industry specifically inside Kusari. It's not the total GDP of Kusari, but it give us a scale of the size of Kusari's economy. If the shipping industry inside Kusari is approximately 1.4 trillion credits per year (with a HUGE margin of error), then it allows us to fathom how large Kusari's economy truly is. Knowing that Liberty's economy is even larger, this estimate can help us imagine just how much money there is in circulation throughout Sirius. I think that's as far as the data will allow me to show.
This is all really bad science btw. I literally just got all of this from seeing that 6 traders happened to have passed through Kusari while I was using TLAGSNET on my KSP.
According to the World Trade Organisation, global trade-to-GDP ratio is approximately 30%. This would suggest that if 1.4 trillion credits per year is made via trading in Kusari, then Kusari's total economy is perhaps around 4.7 trillion credits in GDP.
Of course, there would be differences in shipping via oceans and shipping via planets, so unfortunately, once again, really bad assumptions and really bad science,
but interesting food for thought.
Maybe someone could develop some kind of statistical software which shows us how much specific commodities are bought and sold on each station on a yearly, monthly and daily basis. And how many units of specific ores are mined, bought and sold, each day/month/year. Which ships are the most commonly bought and which ships are the least bought ships (Tigershark continues to be sold at Tangiers but I haven't seen anyone fly one of those since 2013).
It's interesting data to have. Pirates could use it to see which trade routes are the most commonly used routes in order to pirate them. Cops could use it to defend said routes. It would be cool to see which commodities are the hottest on a specific day and compare it with other commodities or other timeframes.