While bitcoins can be exchanged for real currency, 195000 BTC most likely could not be exchanged for anywhere near $147m. This is a significant portion of extant coins; for example, this amount is actually larger than Mt Gox’s entire order book of bids, and much larger than the daily volume on most exchanges.
That said, saying that it is worth $147m is no different than valuing huge stock positions based on the market price.
