You can't just take a save file from 20 years ago and say "let's add 12kb to it and that adjusts for todays standards". There's 0 logic in that. Following the 0 logic train, are you even accounting for cross platform saves? What if it's not one save file, but 1 for each console? Or 1 big save file with the ability for any console to read it? Bare minimum with wild speculation I would say 1MB. That alone throws off your whole calculation and cost by large amounts.

As well, you have 167000 in SSDs which is just... I don't even know. But realistically it looks like you just pulled up Newegg, found the most expensive SSD and said "yeah that'll do it." And when you look at it, you're basically saying "yep, 66 hard drives should cover 20million users pretty well" which sounds equally ridiculous.