I've been combing through the things in my Player's Handbook that I normally gloss over and realized that there's not much distinction between studded leather armor and leather armor. The 5e manual states about studded leather armor:
Made from tough but flexible leather, studded leather is reinforced with close-set rivets or spikes. […] Weight: 13 lbs
And about leather armor:
The breastplate and shoulder protectors of this armor are made of leather that has been stiffened by being boiled in oil. The rest of the armor is made of softer and more flexible materials. […] Weight: 10 lbs
So to my understanding, either leather armor's boiling in oil is something that studded leather armor doesn't have, or the only difference between the two is about 3 lbs of rivets/spikes.
Comparing the price per weight to things like ball bearings, or 5 lbs of iron spikes, the rivets/spikes used in the armor should come out to about 1 gp.
If you had a party member who was proficient in leatherworking and was willing to donate their time, could you transform a 10 gp Leather Armor into a 45 gp Studded Leather Armor for a mere 1 gp?