Patterson tank w/ reels = $30
Mixing jug = $10
Containers to hold chemicals = cheap
The chemicals can develop a large number of rolls
Ilford Ilfosol3 = $10
Ilford Stop Bath = $8
Ilford Rapid Fixer = $8
If you're even cheaper than that...
D76 and whatever the accompanying powdered fixer is called are even more affordable, at like $5 for a gallon of working strength of either.
(ilfosol dilutes to about a gallon as well at 1:9 but coming in a 1/8th gallon container)
And I usually dilute 1:3 and do stand development, which worked better with the d76 for some reason for me, making it about 8x cheaper, not 2x.
And grocery store vinegar diluted 1:3 makes a fine stop bath for about $0.25 a gallon of working strength solution using costco vinegar.
If you do a TON of developing and like the look of "staining developers," look up "obsidian aqua" or other catechol-based homemade developers, which represent about a $50 initial investment for probably more working strength developer than you could possibly use in
years (makes about 1/2 gallon for that much, and working strength is 1:500, so 250 gallons of working strength solution! Plus you still have a ton of leftover chemicals for some of the ingredients, so the next batch is only like $20). And as far as anybody knows, they'll last for years too in storage, if you use marbles to keep out air from your container as you use it up (good idea for any liquid developer that's not mixed each time).
My cost for developing 4x5 sheet film = about $0.05 a shot total. For the same amount of chemicals I can develop half a roll of 35mm film (it has 1/13th the surface area), making each 35mm frame = about half a penny of chemicals.