It's still expensive as fuck once you total everything.
Like if you get into guns because of Upotte, you end up finding out that the associated costs to the gun you buy end up increasing your investment into that hobby.
Gun cleaning, gun repair, tools, ammunition, storage, spare parts, training equipment, holsters/slings, even clothes to match for carrying.
Same applies to swords if you end up enjoying Japanese swordplay.
If you think about it, figs and manga are heck of a lot cheaper, though they don't have as much use as guns, swords, bikes, cars, and motorcycles.
Probably the cheapest hobby you can get from anime is basketball or go/shogi. But then you'd have to find people to play with you.
Boxing and MMA might sound cheap, but there's also gear, insurance needed, gym fees, teacher fees, and a shitload of hours you'll need to train.