How does that make any sense? The average producing cost would be the average price. Right?
Almost NOBODY would farm if the average production cost was the same as the price. No incentive TO farm in that case.
The COST to mine a Bitcoin right now with current gear is quite a bit less than the current price, unless you have fairly high electric cost.
The whole theory of "the production cost = the price" makes ZERO sense, most folks AND ALL MAJOR FARMS are in this to make money, and if the cost and the price on the same THEY CAN'T MAKE MONEY.
The floor at around $400 seems to be more about the major influx of cash in Nov/Dec timeframe when the Chinese markets started accepting fiat currency for purchaces. It has ZERO to do with any "production cost", which is well under $300 and possibly under $200 (if they've replaced most or all of their gear with current gear) for most or all major farms and a lot of home miners. I suspect most of the major farms cost is closer to $200, but I don't have hard figures on the total overhead for any of them (though I have a VERY good estimate on electric cost for most or all of the large farms in Washington state).
The issue for home miners is achieving ROI on the cost of the MINER, which cost is quite a bit higher per hash than for large farms (some of which buy the chips and build their own miners to save on equipment cost, the rest get large bulk discounts, earlier access, and in the case of the farms run by the miner manufacturers like Bitmain they run at least some of the gear for a while THEN sell it for a large markup making their effective equipment cost ZERO or a negative number).