Spread
The difference between the buy and sell price. The wider the spread, the costlier entering and exiting are. Essentially a hidden markup by the service.
In more detail
The spread is a hidden markup: the exchanger buys from you a little cheaper and sells a little dearer. The wider the spread, the more entering and exiting cost you, especially if you swap back and forth often. Comparing the rates of several offices for one direction indirectly shows whose spread is narrower.
