Ok, sorry, I didn't mean to be rude. I'm sure you had the best intentions in mind when writing your answer. The thing is, for me the main reason to ask questions on forums like HN is to work against "unknown unknowns". Things like B2 storage cost can be easily googled if you don't know them, so it makes much more sense to just google them instead of asking here. In fact, that's what is usually expected from anybody asking advice on forums. But the problem is, that in reality there's always more to that than the basic specifications.

Take B2 for example. I know their storage pricing (that's very easy to find on their website), and I know for a fact it's super affordable, compared to other similar services. But I also know, that the "fine print" in their case is just that the upload speed is the bottleneck, which will prevent most users from backing up too much. And the fact that they have only 4 facilities. Is the latter the real problem? Well, I don't know. I didn't hear any stories about them loosing user data, but that might be just it — I didn't hear them. That's why asking such questions on places like HN has value in my opinion.

Similarly with HDD cost. It's kinda obvious that this is the most affordable solution, so if the person asking doesn't know that, it means he didn't do his homework. I don't use my friends' houses for that (that really sound super awkward), but in fact something similar is my current "solution" as well. But it feels like something I should be adviced to stop rather than to start doing. Backup service backend needs maintenance too. And maintaining it doesn't seem like a fun hobby (that's part of a reason why asking a friend to do this for you seems very weird). Backups are something you want to be reliable, by definition. And HDDs are not.

(As a side-note, I also sometimes contemplate if backing up rarely changing info to more reliable storage, like tapes and optic drives is a viable option. It still seems like no, unfortunately. But keeping everything on HDDs that I personally own makes me feel uneasy as hell. Despite being something I do, this is basically a strategy equivalent to "just hoping that everything will be ok". I don't do any real work, to make sure it's the case. I have no idea, when they are likely to fail. I just hope that they don't get broken at the same time, and that's it. I have no idea what the actual probability of that is.)