Impossible to know exactly, but from my experiences buying and selling in the manufacturing sector it comes down to a handful of simple things.
Cost of setting up machines. This costs a similar amount if you produce one or one-hundreds-thousand (there are caveats) So if it costs £1,000 to set up, one costs £1,000 each and one-hundred-thousand units costs 1 pence each.
To a lesser extent the same applies to bulk purchasing of the materials.
The second significant factor is selling on value over selling on price. You can buy new guns for £600, £6,000 or £60,000. There is a similar amount of material in each. The more expensive gun will cost more in material because the maker will pay proportionally more for their smaller volume of material, but the difference won’t be anything like close to 100 times the amount. The luxury gun of course will have a lot of hand finishing work involved, but accounting for the time/labour The £60,000 price ticket is a lot more to do with brand than actual Cost of Goods Sold.
If you take grade 4 wood and compare to grade 10 for example, grade four may “cost” £2,000 for the finished stock and fore-end, while a grade ten might be three or four times that. Mechanically the same, same amount of effort to to shape, though the latter is more likely to involve more manual skill and the former more automation.