Cuz rackmount stuff is usually cheaper, and I find it hard to believe that you could put 10 grand for a mobile DJ into rackmount stuff.
Most expensive dual rackmount is 1,000$, assume another 1,000$ max for a mixer, which would be very expensive for what a mobile DJ would use. Another 500$ for crossovers and EQ's. And DJ lighting is almost always simple DMX controllers which are pretty cheap, so we can assume 500$ max in controllers.
And how many speaker sets were ya using? This helps me figure out the value of what could possibly be on a 10,000$ mobile DJ rack.