OP was asking about the end of 2014.  $1500 for the end of 2013 seems about right at this pace.

Many people are predicting that it will be around $10,000 by the end of next year using a logarithmic growth chart.  I think the trend line is a bit low though.  Basing on the growth that has happened this year we are looking at at least $10,000 by the middle of the year and close to $100,000 at the end of 2014 if the same rate of adoption happens next year as it has this year.  It seems crazy, but going from $10 at the beginning of 2013 to $1000 now would have seemed crazy to everyone too!

Regardless, it should be an interesting year for sure.