Its basically 5 full blocks.
If only, OP_RETURN only takes 40 bytes. So if you made a smallish transaction it would be 10% of it. So something like 50 MB to do it.
If you did it 3 times a day you have consumed the more than entire block bandwidth.
It could also be encoded in addresses AFAIK which takes less space. I was assuming perfect use of block space, which of course is not realistic and an actual solution would waste even more space. The white paper by satoshi is said to be in this transaction[1] which has only ~7% overhead.