Hijinks income MASSIVELY outpaces other Income Sources?

So I have a high level campaign going on and one of my players has a criminal guild that we were rolling hijinks income for. In our case he has 10 thieves that we use the average for a 3 that we roll for one at 5th level. We can ignore the slew of carousers and such for this discussion.
It seems to me that the income potential for a criminal guild vastly outpaces other campaign activities.
-In a Class 2 city it costs me 200 gold of investment in my hideout per ruffian I wish to be able to hire.
-I can hire thieves with little no upfront cost provided I can put them to work immediately and their jobs on average cover monthly salary.
-A level 4 thief after cost according to the table in Acks generates 425 gold per month
-with some variance for what part of the month you hire them for a cost of 2,000 gold to establish a hideout I can arrive at a city with capacity for a thieves guild and hire 10 4th level thieves at an average of about 3 a month. again with cost mostly covered depending what part of the month you hire them in meaning they don’t really add any required investment to get this rolling
-even just getting 10 of them over 3 months means I am making over 4000 gold a month with basically a 2000 gold investment.
For reference the new update to mercantile ventures puts a 10,000 gold investment in a small ship at a value of 800 gold a month. A perilous investment of 10,000 gold that does average will be worth 900 gold.

When I do the math to try and calculate if the average for thieves of varying levels is accurate I come to them being worth closer to 1400 gold per month on average if they are a 5th level thief spying.
Am I doing something wrong/ missing something or is this supposed to be this unbalanced?

*note if you’re reading this please focus on my first post as that is the one that matters, I added this for interests sake and have seen the posts where the method used to calculate the average is used. This just shows that profit for a PC who chose spying for his 4th level spies will likely be even higher than the average provided in ACKS that I used for the math in the above post.

To elucidate on my point that my calculate average comes out higher I thought I’d show my math so people can see what I’m doing and point out any mistakes. This is my math for a 4th level thief spying.
-At fourth level a thief needs a 16 or higher to succeed which is a 20% chance
-they earn 2d12 which on average is 13 gold multiplyed by 100 multiplyed by their level (4) for a total of 5,200 for a success
-20% of 5,200 is an average income of 1,040 per month

Expense: I have assumed highest possible expense with weighted averages.
If caught punishment is determined with a d6 1-3 is tried for eavesdropping with a highest penalty of 25gp and imprisonment, on a 4-5 it is loss of the spy which costs 125gp to replace, on a 6 it is the same as before 125gp to replace. therefore I can multiply each cost by its likely hood of happening.
Overal they are punished on a roll of 1 or if they fail by fourteen or more in which case they are punished on a roll of 1 or 2, meaning there is a 10% chance of punishment.
-3/6=50% multiplied by 25g = 13gp
-2/6=33% multiplied by 125g = 42gp
-1/6=17% multiplied by 125g = 21gp
-Cost of bribes = 1,500gp
-Cost of lawyer = 100gp
-Cost of Restore Life and Limb if maimed = 500gp
Total Cost = 2,175 multiplied by likely hood of failure (10%) = 218gp

Profit = 822gp
if Restore Life and Limb cost double in the case of not following that churches religion profit becomes 772gp.

nearly double the average provided which as above unless I’m missing something seems far more profitable than other endeavors. This calculation also didn’t factor in the ability to hire replacements part way through the month to whose earnings have the potential to negate the cost to hire them which would mean that the cost of rolling sedition or treason as punishment could potentially be less costly overall than rolling eavesdropping. I left that out as I understand that a ruling could be made that mercenaries purchased in a month can not be assigned hijinks for a partial month.
This ruling would also add some upfront cost to the investment figure in my above post but even adding that extra 1,250gp of cost still leaves it leagues ahead of mercantile ventures or investments.

Got some guidance when I posted this on discord. Short answer was that the availability rules work best for occasional visits to multiple locations by adventurers and can be abused if used month over month in a similar location.
The gist of what I got was that hiring new thieves likely involves poaching them from other syndicates and the campaign pressures of those interactions should serve to both limit the speed of growth far beyond something a static availability table takes into account. Also the reactions of these syndicates will likely incur further costs as well.
My solution will likely be to require a more varied guild with higher level spies being very difficult to acquire as they are valuable assets to their current syndicates.

I also wanted to share perhaps the most illuminating part of the discussion from Archon himself.

“All of the mechanics assume things exist in hierarchies
The biggest empire has the biggest city
The highest level thief has the biggest syndicate
To the extent that’s not the case, odd things can happen. and that’s ok!
BUT what is important is that you, as the GM, realize that the world “tends to equibilirum”
and that equilibrium is one where might makes right, where the powerful people are the most badass people, and vice versa
and where things get organized hierarchically
so –
a player character finds an amazing piece of land and starts an incredibly profitable domain. Awesome! for a while he’s the richest baron around. then what
you as GM to keep the world a living word, folks need to react to that.
a player character hires every spy in every town to create an incredible spy network and gets rich fast. Awesome! for a while he’s the spy king. then what?
all the rules can really tell you is, “all other things being equal, if this happens, and we hold everything else constant this will be the outcome”
but in a campaign, you the GM shouldn’t hold things constant.
I tried to model this dynamism in some places in the rules, but didn’t do so in the syndicate rules, and it shows! so mea culpa”

So that answers all my questions and closes this thread as far as I’m concerned.