Personal/consumer-designed printers shouldn't be compared to commercially used ones. You can imagine that a large company will not use consumer printers. They need to produce thousands if not more of those barrels and such printers will cost a fortune. This one below is more than 10 gran (not the most expensive), and how many of those printers you might need to make large quantities of barrels? What company wants to invest in such equipment?My son makes resin 3D parts, and I've had him make small parts, barrels, etc. for me. The actual cost of a quality resin barrel is pennies, and dozens can be made at once with no one in attendance. Brass is more expensive as is the process of machining or casting them. I prefer the heft and sturdiness of brass, but if the sizes and shape are not accurate, would prefer 3D resin.
Most brass barrels on the market are CNC-turned, not cast. HIS Model makes CNC-turned barrels in a close match.