I'm looking for a rough estimate on how much it costs. I understand that it is a propellant mix, and that NASA contracts a company to produce it, but I am yet to come across a figure per kg of the fuel.
According to this NASA fact sheet about the Shuttle and its propellant, the total cost for fuel was:
At liftoff, an orbiter and external tank carry 835,958 gallons of the principal liquid propellants – hydrogen, oxygen, hydrazine, monomethylhydrazine and nitrogen tetroxide – currently costing approximately $1,380,000. Their total weight is 1,607,185 pounds.
Using that total weight and the total cost, you're looking at around $0.85 per pound of fuel.