I thought some miners had said their cost level was around $150. But that was many, many months ago. I guess they'll have upgraded equipment since and the difficulty hasn't done that any favors either.
$150 used to be the bare minimum cost + profit for miners, that was in late 2014/early 2015. As you mentioned, the equipment cost and dff factor has gone up quite a bit since then.
I'd guess $450 is the new, bare minimum cost + profit for most miners, below which it doesn't pay to mine any more. After the halving, the price of a bitcoin should be around $900 or else the miners will start turning off their gear.