I've seen that with many other breeds too, supply and demand, more people want bitches, simple as that.
There's also quite a big demand for borders so it pushes up the price, free market economy, it filters down to everywhere.
If i was selling a litter of pups then i'd want the going rate unless it was to a friend, a good homes more important than cash but who the hell is going to give away pups to people they don't know. The person you give it to may just be a chancer and think well theres nothing to loose with this one for free and i can just sell it on.