1L of developer, which I rate conservatively as being good for 8 rolls of film without any replenishment steps, contains $1.15 of chemistry, so cost per roll would be about 15 cents. This is based on Stefan4u's Flexicolor clone formulae post on this site back around 2009.
Stop bath is dilute glacial acetic, mixed to cost 7 cents per litre, used once, so if 4 rolls processed at once in a 1L stainless tank, it costs under 2 cents per roll.
Bleach is currently free for me. I am using up some e-6 bleach, found at the 'pick fo free shelf' at my HHW depot.
Prior of that I used c-22 bleach, which is a ferricyanide and bromide mix, costing me about 15 cents per roll; 2litres of this stuff, with one litre acting as replenisher for the other working litre does 22 rolls.
Fix is derived from bulk ammonium thiosulfate, and costs perhaps 10 cents per roll, if a litre is used for 15 rolls, which is approching its exhaustion point with c-41 films.
I count photo flo as free.
So that put my processing cost for a c-41 film (i.e. the classic 80 square inches) at 42 cents per roll if all solutions I mix are used to capacity.