That being said, we are not in 2014 and the price is relatively high at a 129 billions $ total valuation of BTC in circulation. Remember when it was in the 200s for a while ? It was a valuation of a few billions, it went up 35 fold.
I remember a time when 1 bitcoin was worth around $12. I earned 0.01 btc through faucets. A user on this forum named Otoh gave me 0.09 so that I could have 0.1 btc. (I still intend to pay him back for that someday, btw) Having seen bitcoin at $10-$12, it would be very easy to assume bitcoin was a bubble @ $200.
There's no doubt that bitcoin was $200 not long ago. The question as to whether bitcoin is a bubble may revolve around whether bitcoin was severely undervalued when it was priced @ $200. If btc was significantly undervalued (which it may have been) recent price gains could be sustainable.
There can be significant lag time between fundamental growth and actual price movements.
Bitcoin's high before $200 was $1,000+. It dropped from $1,000+ down to $200, if I'm remembering right. This could be evidence that bitcoin was severely undervalued @ $200. Its real value might have been more than $1,000.