That would depend upon the provenance, what is currently happening in Gettysburg are dealers selling bullets that say that they are from Gettysburg. While this may be true, it is misleading as the bullet is in Gettysburg, but not necessarily from the Gettysburg battlefield. A bullet purchased in the park with a vintage label would be worth much more than one by itself.
Back in the 70s when I was myself a youngster, my uncle built a metal detector for me, well we had to test it, so off to Gettysburg we went. We were very naively hunting around the copse of trees and found an incredible amount of detritus, when a very heavyset ranger came from the direction of the maintenance building huffing and puffing. He realized we had no clue as to what we were doing and asked if we found anything, I handed over a watering bit I had in my hand. He replied that it most likely belonged to a farm animal, but he needed to confiscate it and that he could impound the detector, car and fine us $10,000. We asked where we could go detect and he gave us directions to the house of one of the most successful hunters in the area. I was wearing military fatigues with multiple pockets full of buckles, bullets, bayonet and shrapnel pieces and waddled off to the car. The kind ranger had to know, but let us go on our way. We went to the house of digger and he welcomed us in and explained how and where to dig, he graciously showed us his collection which was enormous, I wish I could remember his name, IIRC he lived on Taneytown Rd.
Well some years later I went off to college and mom threw out all of those artifacts...…..