Hey. Here's a tip.
If you're going to extrapolate an exponential curve, save yourself some trouble and use a logarithmic graph.
For example!
Edit: Let's say you're willing to throw caution to the winds and assume that the first meteoric rise in USD per BTC is representative of such rises in general (I think this is a foolish assumption at best, but whatever, let's roll with it). In that case, we can overlay the graphs, and...
...call the top at somewhere between 250 and 400.