If I ask you how much the BTC is worth right now, what is your reference? What will you base your answer on?
Now, try think outside the box (I know it is impossible, but one may still try) and explain how this works.
So, what makes the value of a BTC any less subjected to the same manipulative forces than fiat currency is subjected to?
The reference I use to value bitcoin is the same used to value the other currencies: How successful the economy that support it is, and will be in the future. Usually this is measured by some factors like total revenue, money velocity and inflation. Total revenue in bitcoin just now is ridiculously low, less than 3% of Market Cap monthly, but there are people that are confident in a great growth potential, and speculate based in this future value.
In normal currencies the ratio of daily commercial transactions to speculation is usually so high that the exchange rates move comparatively slow following the speculative trend. However for bitcoin that ratio is inverted, speculation is 97% of volume, and the exchange rate is based on speculation about its future value, like it happens with stocks. If/when revenue growths enough or speculation is tempered by reality checks, bitcoin value will go back from its future value to the intrinsec one (ouch!)