The speed isn't lost by half, but it does slow down a lot. I remember reading that a tennis ball from a flat high speed serve leaving the racket at 130mph, is down to 70mph by the time it's struck by the returning player, aerodynamic drag is part of this, and the bounce off the court is the rest. A "slow" court surface slows the ball down more than a "fast" court surface.
With the new string technology, serves have more topspin than before, especially second serves, and the speed loss from the bounce is not as great. Unlike table tennis, the surface speed of the ball from spin won't be faster than the speed of the ball, except for backspin (slice) shots.
I responded to your table tennis post, it might be interesting to some here.