There is a math error in that.
25 x 25 feet is 625 square feet, which is 25 square feet each for 25 chickens.
10 x 10 feet is 100 square feet, which is 4 square feet each for 25 chickens.
So if 30 chicks each eat 20 pounds of feed that's 600 pounds of feed
At 50 pounds per bag, that's 12 bags
Times $20 per bag is $240
I rounded the feed consumption up a little to make the math easier. You might still need more than this if you have large breeds (brown egg layers). If they waste...
I don't know the cost of your feed, but if you can tell how much each chick will eat, you can then price the feed and figure it out.
Here's one estimate:
https://extension.umn.edu/small-scale-poultry/raising-layer-chicks-and-pullets#economic-considerations-1704561
"From hatch to 20 weeks-old...
Do you know how many eggs your household currently uses per day or per week?
If you do not already have experience with chickens, it is usually best to start fairly small, rather than jumping into a big project right at first. I would think somewhere between 6 and 25 birds is a good starting...
Just make sure you do the math first-- cost of chicks and maybe shipping them, cost of chick-specific feeders & waterers, cost of chick food, cost of heat plate and electricity, maybe cost of your time to tend them as they grow up.
Even considering all the costs, chicks probably are cheaper...
If you need eggs soon: started pullets.
If you have a good source of started pullets: go for it!
Otherwise, chicks.
Given that you need 50 to 60 of them, raising your own chicks is probably more cost effective.
Build your coop FIRST, then get 2 heat lamps and a few chick waterers/feeders and...
I suggest you get 50 chicks. It's a nice round number, and with those breeds you should get more than 25 eggs most days from 50 females, but you won't get more than 50 eggs.