An "economist" opinion means nowadays zero, or 0.000001 if he has a twitter account. We all know what happened in 2007 and how economists were able to estimate s***. And the ones that did manage to get things right screwed up 20 times after.
Lets's start:
https://blockchain.info/charts/estimated-transaction-volume
And at this point...arguing about it useless.
But let's do the math with his own method but real numbers.
Since the value of transactions is 2 billion a day (based on the same damn newspaper the guys write for link
We would have to increase the price once 20 times and again 30 times.
Leading to a value of ...surprise 12 000$
PS.
bbc.reporter I'm sure you understand I'm not arguing with you but with Mister Richard Jackoff