If you refer to some of the original purchase orders - and it has been years since I was lucky enough to see them thanks to a collector who had access to some of them - the Federal Government was purchasing 1860 Colt Army pistols at $25.00 each. (Political kickbacks not listed). Evidently, these contracts did vary in what Colt was paid. When Remington started to supply their New Model Army revolvers to the Federal Government in 1863, they undercut Colt's price by 50% - i.e. $12.50 per revolver.
One also has to remember that the price of ammunition and firearms would most certainly have varied depending on the location. Most things were shipped by rail once the railroads were established. They didn't ship for nothing so the shipping would certainly have been reflected in the price of ammunition and firearms. As an example . . . the price of a 44-40 round in say, Kansas, would certainly have been higher than the same round that was produced and sold in close proximity to the manufacturing plant.
My grandfather was born in 1867. He married my grandmother in 1901 - he was 34 and my grandmother had just turned 18 - she had taught one year in a one room school. In 1920, my grandfather built a new house for them. He was involved in farming, was half owner of a lumberyard - a variety of things. I still have the handwritten ledger he kept for the construction of that house. In 1920, he was paying the master carpenter a wage of 22 cents an hour. Most weeks, they worked six days a week - so say if they worked a 48 hour week - the master carpenter would have made $10.56 a week - times 52 he would have made around %549.12 a tear, The general Laborers on the job - who wold have received their instructions for work form the master carpenter - they were paid 17 cents an hour or for a 48 hour week - $8.16 a week or times 52 - $424.32 a year, And just in case you're wondering if the age difference between my grandparents mattered - it didn't - they were married for 62 years at the tie when my grandfather passed away in 1963.
I have often wondered what a pound of black powder cost in the days the OP is asking about. I cold buy a pound of Dupont black powder in the early 1960s for 75 cents a pound - in fact - I still have one of the cans with that price marked on the top with a black grease pencil - and I'm guessing that many of the younger ones have never seen a "grease pencil".
In the early 1960s, we could walk to the local hardware and buy a box of 50 22 cartridges for fifty cents plus 2% wql4w tax - the hardware usually carried Winchester or Remington brands. My Dad insisted that we buy "shorts" because he would show us the printing on the flap of Longs and Long Rifles - "Danger - Range 1 Mile". Shorts were fine with us as we had no problems taking rabbits and squirrels with them.
It would be interesting to see some advertisements from the 1870s and 1889s from different locations to see what certain ammo was going for. It would also be interesting to know how many folks bought the Ideal reloading sets - cast their own and bought powder and primers to reload their own to save money over the cost of commercially produced ammo.