If i think from cost perspective of Langar 24 X7 on Akhand Paath days
From My experience in Asutralia
This is for normal Gurudwara where Avg Sangat on sunday is around 700 ,
Friday morning - $100
Friday evening - $200
Staurday Morning - $300
Saturday Evening - $500
Sunday Morninng - $1000
Othercost like Degh, Dishwaqsher etc = 200$
$2300 for Langar and all that
Then its shrada of various Pathi Sings or Gainis who have to do paath.
If there are at least 4 Gaianis and you give them 300$ then $1200.
About 3500$
If that Gurudwara is Big like in sydeny cost can easily go to 8000$
Again it can be up and Down
Even if Gaini ji dont take any money even then i think the min cost will be around $2500 or more depending upon Gurudwara Sahib
Cost can reduce if you are doing inside your home but again then you have to pay to Giani Ji for their rauls