You can brew way more than 19L a month. Hell you can brew 19L a day if you have time and room for it and want to drink that much, or have that many friends. Ingredient costs vary by what type of beer you're making - higher alcohol takes more grains, big hoppy IPA's take more hops etc. Liquid yeast costs more than dry yeast. Its been a long time since I really paid attention to my per batch cost which I'm sure has ben hit by inflation like anything else, but a standard simple pale ale or the like is probably still less than $30 in ingredients. Like anything, cheaper to buy in bulk.
I guess prices have gone up slightly but they are on sale right now. This is what I brew on currently. Used to have a big 3 pot, 2 burner, custom welded propane setup that took up half my garage. This is way easier and smaller. Not much else you need beyond this that is mandatory besides a fermenter which can be as simple as a 5 gallon bucket. Like fishing you can go way down the rabbit hole and get fancier glycol chilled this and stainless that, but at the heart of it you need a boiler, a mash tun,and a fermenter. The brewzilla is the first two in one.