Cheap DJs might not legally purchase their music. This means that songs can be mislabeled in title, ormislabeled as ‘clean’ versions when they are not. Illegal downloading makes it more likely they have a virus on their computer, which could shut things down at any moment.
Cheap DJs might be nervous on the microphone. If the DJ is uncomfortable, EVERYONE is uncomfortable.
Teenagers can be very picky with the music they request. Cheap DJs may not know how to handle that age group, or come across rude.
Cheap DJs might not keep their music updated to be able to play requested music, much less the clean versions.
Cheap DJs tend to have other full-time jobs. This divides their attention, preventing them from following up on, and keeping track of requested details for your event.
Cheap DJs might not know how important it is to keep their vehicles in good shape until they find themselves broken down on the way to a gig. I learned this lesson the hard way, and it was back when I was a cheap DJ.
Cheap DJs might not have redundant equipment. If a mixer, computer, external hard drive, speaker, or amp blows, the party’s over.