Current mining:
Difficulty: 7,672,999
62,172.58 GH/s
969.89 megawatt hours
$145,483.85 / day
3600 bitcoins created / day
$145,483 / 3600 = $40.41
If you want fundamentals. You cannot charge less for a product than it takes to produce.
But for every product you buy you have to consider:
cost of production + cost of distribution + cost of retail + cost of marketing at the very least.
Price rarely dips below difficulty for this reason.
Doesn't this presume that only miners are selling bitcoins? 11 million coins out there. Miners find 3.6 thousand per day - i.e. miners find a minor (pun intended) .032%/day of what already exists. In a month, they still only find a mere ~1% of what already exists. There seem then plenty of bitcoins subject to selling pressure by those not incurring the expenses of mining. So, I'd think that it could drop below $40.41
I will assume forex follows most of the price patterns of stock trading. What did Jesse Livermore - trader extraordinaire - say about how low something can go?
"Remember that stocks are never too high for you to begin buying or too low to begin selling."