Paypal 2012 estimated earning is around 2.2 Bln $, i used a P/E of 10 to compute the market cap, considering that since 2002 Paypal isn’t anymore a public company but was acquired by Ebay.
Actual Bitcoin market cap is 115,745,249 USD or 91,561,260 EUR
Bitcoin Trading Ideas, Analysis 
I think the miner profit will be an important factor. If bitcoin reaches $100 or more, how competitive / what difficulty the mining would be? thankfully 8/12 years later it will be 6.25/3.125 BTC per block… so it wouldnt hurt if one bitcoin worth $1k or more, as the difficulty will be high enough.