Did you ever test your model? I don't mean the error you produce by taking the learning data. I mean the actual prediction for an at that point unknown future. For example: You are prediction 489.2$ for tomorrow 4pm GMT. Now save that prediction and compare with the real value tomorrow.
I think then you get a much larger number than 1.3%
I think this is because the error adds up. So 1.3% only applies to the forecast of next hour and when you predict for example 12 hours ahead you could end up being 15.6% off.
It could propably be helpful to give additional information like average error of predicted price 6/12/18/24 hours ahead. That gives a better impression of the capabilities of this model.