I don't want to go into too many details for obvious reasons but you really do not need to spend a 2000$ on an amplifier to get more than 10 feet of range if you are building say a DIY IMSI catcher.

Just suffice to say are over the counter (if you are willing to order from china, or heck Dealextreme) cell blockers and boosters that cost <200$ that can block cell reception over a much much greater area than a 10 ft radius.