Can anyone advise on their typical cost for using Uber?

I used it for the first time last night in Chch out of necessity. I was with two others using the UberX option. We were driven for ten minutes just 6km and it ended up costing little over $30. It was midnight on Saturday. Seemed pretty expensive to me but I have no point of reference. It's way above what the fare estimators quote but I don't get how this "surge pricing" bs works.

Thoughts?