I don't spend a lot on grinding belts (I mill)
I don't spend a lot on endmills (I use older endmills for this, and intelligent machining strategies)
I normally don't spend too much on scales (I use good quality, but normally relatively plain wood or micarta)
I use excellent steel, but there just isn't that much steel used in a knife.
My heat treat setup was thousands of dollars, but that was an expense I had before I got into knifemakeing.
My knives are mostly milled, don't ask what CNC mills cost, but again, that was an expense I already had.
Leather is not that expensive
Stainless foil is not that expensive (argon can be, but I stopped using that)
Sandpaper is not really that expensive
None of it is really that expensive. The total cost in a simple knife, including machine depreciation and electricity (hidden costs), is about $40. The single largest expense might be endmills, but I'm using cutters leftover from other work. Otherwise, $60 divided over ten blades would be $6. Steel about $5. HT about $4. Scale material can vary widely.
My single largest "expense" in knifemakeing is time. I have turned away better paying work to make knives. I don't regret doing that.