That's what 20 MB blocks require. That means, you receive the blockchain, that's 84 gigabytes per month. You send the blockchain to one peer, that's another 84 gigabytes per month.
This post is very misleading.
Just because block sizes are allowed to be 20 MB doesn't mean they will. That would take a hell of a lot of transactions to create a 20 MB block.
If the block size was 20 MB right now then it would make no difference if there's still only 500-2000 transactions per block.
By the way if we do start seeing 20 MB block sizes at some point in the distant future after they have been enabled the time to increase this limit from 20 GB to 40+ GB block sizes will have long passed.