The current global break-even cost of mining a bitcoin is $8,038 according to FundStrat Global Advisors reported in an article in MarketWatch (https://www.marketwatch.com/story/heres-how-much-it-costs-to-mine-a-single-bitcoin-in-your-country-2018-03-06) using data collected by a company called Elite Fixtures (https://www.elitefixtures.com/blog/post/2683/bitcoin-mining-costs-by-country/).
The minimum cost of mining a bitcoin is $531 in Venezuela.
The maximum cost of mining a bitcoin is $26,170 in South Korea.
The cost of mining a bitcoin in Russia, USA, and Iceland are all around $4,700.
All dollar amounts are in USD.
McAfee told us in September 2017 that it cost "over $1,000" to mine a coin insinuating that the mining cost puts a bottom limit on the value of a Bitcoin (https://www.cnbc.com/2017/09/13/john-mcafee-challenges-jamie-dimon-bitcoin-skepticism.html).