I can't speak for all exchanges, but most (including Nasdaq) charge once per display device/platform. That means if you are getting data through two platforms (eSignal & RealTick, for example) you'd have to pay twice. If you are getting data through two devices from one vendor (say, eSignal on your PC and via a Blackberry) it can be counted as only one if the vendor can prevent you from using both devices at the same time. Anyone who tells you that you can avoid paying more than once is misleading you.
In market data speak this issue is known as "MISU" (Multiple Instances for a Single User) and has always been controversial. At Nasdaq we are trying to address this somewhat with respect to TotalView, our full-depth data product, with large vendors through enterprise licenses and other pricing initiatives. We have less flexibility on this for Nasdaq Level I & Level II data, because technically Nasdaq doesn't own it (the "UTP Plan" that is comprised of all exchanges trading Nasdaq stocks does).
William O'Brien
SVP, Market Data
Nasdaq
In market data speak this issue is known as "MISU" (Multiple Instances for a Single User) and has always been controversial. At Nasdaq we are trying to address this somewhat with respect to TotalView, our full-depth data product, with large vendors through enterprise licenses and other pricing initiatives. We have less flexibility on this for Nasdaq Level I & Level II data, because technically Nasdaq doesn't own it (the "UTP Plan" that is comprised of all exchanges trading Nasdaq stocks does).
William O'Brien
SVP, Market Data
Nasdaq