You can find cheap ink, and expensive inkk. More expensive bottles are sometimes larger, but other times not. The price range of inks, I’m talking about fountain pen inks by the way, vary from around $5 to a little bit under $40. The cheapest from JetPens is about $0,55 per ML while $0,74.
If you compare the price of ink to the other part of this that you actually use up - paper. Then you will realise that ink is not that expensive. When I wrote a lot with and exclusivly with fountain pens, I used maybe close to three 50 ml bottles a year, but I think most people would struggle with using one a year. I don’t know the number, but imagine how many notebooks of your choice you need to buy to use all of that ink.
If you use Pilot Iroshizuku inks and Leuchtturm1917 notebooks, you spend about the same per bottle of ink that you spend on a A5 notebook, but I think you need at least 20 notebooks if not more to use all of that ink.
I get that some people don’t have that much disposable inkcome, and I get that those of you that this applies to have some different priorities, but I personally went with Pilot Iroshizuku inks even when I was on a tight budget because I enjoyed using it so much more than cheaper inks. If you like me have some disposable income to use on this hobby, I think there are much better places to how much money you spend than inks. Because you get a bottle and it lasts forever. Notebooks are a place where you can save a lot of money. And not buying pens are another.