You charge for deleted file retention like it's any other thing that takes up space and let the customer decide how much they want to pay for. Some will want t

You charge for deleted file retention like it's any other thing that takes up space and let the customer decide how much they want to pay for. Some will want to pay for "5 years" worth, others won't care. To be extra good about it, maybe do it like borg backup and others and save the changes with dedup and compression. You can have literal years of file retention and have it take up less space than you think it would.