I've attended dozens of workshops and they are all over the map in respect to price.
The criteria for me, is not what it costs but what will I get out of it. Some are actually life changing, and others are an insight into another photographers methods.
Some are hands on, and others are more instructional.
I will say that today with the internet and the availability of buying DVDs there are cheaper ways of learning than workshops, but with a workshop you can often learn a great deal from being totally immersed and you can learn from the other participants.