That s quite a difference, and it would be very tempting to choose the cheapest alternative. If that s all you can afford, than you have no choice. But, consider the law of supply and demand. There is a reason some DJs charge more money than others. They are usually worth it.
More expensive DJs tend to be the more experienced DJs.
They can charge more because they have a lot of jobs, and they have a good reputation. Generally, the DJs on the low end of the price scale are new to the business, and trying to get established. They could to a great job, and might be worth a shot if your party is on the informal side. But there is probably more risk with a less experienced person. As you speak with the DJs, pay attention to their professionalism over the phone.