A viable 3d printer can be had for as little as $150, but it will be a kit, and require you to do assembly and calibration, once those are done however it would be a very capable printer easily able to make this magazine, in the $350-400 range however you can get ones that have a much larger print volume, and quality, plus are almost assembled, 20 minutes from unboxing to printing instead of 6-8 hours. and require no calibration. Now im not saying buy a printer just to make the magazines, that would be pretty dumb, but, if you already had the printer, printing the magazine would be so much cheaper then buying one, if you already had a printer you likely could make 20-30 of them for what 1 purchased one would cost. And the files are not that hard to find once you know where to look. and they have a lot more magazines then just this drum, they for instance have one for a ak-47 as well in the same file set, as well as many other rifles and pistols. And i have seen files for speed loaders like the uplua, as well as other kinds, racks for storing reloading supplies, IWB holsters for various guns, and other types of holsters like ones for under the dash in a car, ones that can go back and forth between under the dash and IWB even. Pretty much your imagination and it having to be made from plastic, are the only limitations.
Considering that drum magazines are at least $100 from midway or brownells, your not far off the price for a kit printer, and it is more then able to make the drum magazine. buy 2 drum magazines and you are over what you could have gotten the printer for and printed both. As to the durability of the printer magazine vs the purchased ones, you can print them in abs plastic, and even tougher plastics then abs, so they would be just as durable, if not more so then purchases ones that are made of plastic. clearly metal ones this wont apply to.
The only real difference in sub $1000 printers, and really even over $1000 printers that are the filament based ones, meaning they heat up plastic and lay one layer of it on top of another over and over again to make a print, is, the more expensive you go, the less setup work you have to do, and the better quality or speed at the same quality you get, but another class of printer exists that uses a laser to fuse a material into a solid body, this can even make things transparent as glass, as strong as carbon fiber or even steel, something the filament printers cannot do, they can make things that are very, very strong, heck people have used the FDM printers (filament ones) to print guns, so they can make very strong prints, i've even seen bump stocks you can print, but they cannot make things transparent, so you would not have a magazine with the ability to easily see through it. but the laser based printers can do that, plus make even stronger printed items, these are the printers car manufacturers use to prototype a part that they then use on a car for testing, those however are in the $5000+ range, not exactly a hobbyist purchase. And several companies are working on printers that can print actual metal now.