Why does a package without Sound & Lighting cost almost as much as one with?

Generally for events, DJs require the following: 1) CD Library and/or Laptop; 2) Microphone; 3) CD Player and Mixer and/or Laptop Contoller; 4) Wires; 5) Speakers; 6) Lighting when booked. As you can see, if the DJ is performing at a venue where you have instructed them to patch into an exsisting sound system, they are still bringinig almost the same amount of equipment, and only spending 10 - 15 minutes less of set-up and tear down time. We are one of the few DJ companies that will give you the option to book the regular rate to include us bringing speakers as backup, OR offer a discount without. If you choose not to have backup equipment, we will book the smallest rate (as number of guests does not affect us) with a  discount. But I do stress that asside from not bringing a pair of speakers, our level of service, and the support we provide is exactly the same!