With a bit of patience, I've seen external hard drives as cheap as $25 per TB (so that's $200 for an 8TB drive).

That puts the cost of storing the entire 84.5 GB blockchain today at about $0.265.

It's really getting pretty silly when people claim that the blockchain is going to get to big for anybody to be able to afford to store.

With growth of 1 MB per block, the incremental cost if hard drives never get any cheaper will be about $0.1643 per year.
That means in the year 2140 (when the last satoshi has been mined) the total cost to store the entire blockchain will be about $20.65.
If people are still using bitcoin at the turn of the millennium (the year 3000), AND if hard drives never get any cheaper, the cost to store the entire blockchain in the year 3000 will be about $162

It gets a bit more expensive (if hard drives never get any cheaper) if blocks are allowed to grow to 10 MB per block.
In that case, the incremental cost will be about $1.643 per year.  By the time the last satoshi is mined (when we are all long dead and gone) in the year 2140, people will need to spend $200 on an entire 8TB hard drive to store the full blockchain.