Estimating the "true" worth for 1 BTC and one-month forecast by chart curve-fitting

There are 5 lines on the chart representing different approaches.

The green line gives the most pessimistic estimate, a bit over $20. The point A and B of this line goes from May 2012 to mid-January of this year to disregard the recent skyrocketing of the price.

The blue line has most optimistic estimate: almost $140. It is a true curve to reflect the recent exponential growth, but it ignores the price after late-March when it got really out of hand.

The red line is similar to the blue one but has a more conservative curve. The purple one is a linear estimate following the trajectory of the month of February and disregards the exponential growth that started in March.

The yellow dashed line is the median estimate, just under $80. If the true growth is linear and we go with this line, the price should increase around $20 a month, arriving at $1500 in 4.5 years.

It will be interesting to check back on this chart one month later to see which line gives a more accurate forecast.