The software borgbackup does some insane compression.

It is more effective if you backup multiple machines tbh (my 3 linux computers with ~600gb used each get compressed down to a single ~350gb backup, because most of the files are the same programs and data over and over again)

But it might do a decent enough job in your case.

So one of the solutions might be getting a NAS and setting up borgbackup.

You could also get a second one and put it in your parents or best friends home for an offsite backup.

That way you don't have to buy as large of a drive capacity, but will only have fixed costst (+electricity) instead of ongoing costs for some rented server storage.

I guess that would be about 400$ per such a device, if you get a used office pc and buy new drives for it.

Tape seems to be about half the price per TB, but then you need special reader/writer for it, which are usually connected via SAS and are FUCKING EXPENSIVE (over 4000$ as far as I can see).

It only outscales HDDs in price after like ~600TB