This is a bit raw as statistics but should be close enough as a historical reference:October 2013 KnC Jupiters started to ship: As you can see difficulty was still low enough for 580 GH/s+ miners to mint over 1.5 BTC / day
Bitcoin price was heading from $200 to over $1200 (would get there in less than 2 month):
Around a month later, November 2013 difficulty jumped up x3 with Bitcoin price hovering around $340
where 1TH/s miner would still yield you close to one coin a day. Those early KnC Jupiters would pay for themselves by now and were becoming money printing machines.
Today, a year later, you would need around 80TH/s miner to mint 1 BTC and consuming over 40KW of electricity per day with over $20,000 invested in hardware.
NOTE: A Big Thanks to
https://bitcoinwisdom.com/bitcoin/difficulty and their wonderful stats and graphs.