They are owned by different companies, they all operate differently. That's a very broad question. Some you rent and don't buy, some you buy. Average price of the software is around 4,000 for a reporter and about $1500 for a scopist.
The most pupular are Case Catalyst by Stenograph and Eclipse by Advantage software. You want to buy the software that most reporters use, hence more clients. If you invest in a software that not all that many reporters use, you lessen the pool of clients. Something to think about.