So, is that what you consider your job title -- professional salesperson?
If so, then you are neither a DJ or entertainer. You are simply trying to get as much money as possible out of people, by doing whatever you can to get it. We generally refer to folks like that as "hustlers"
Products generally come with services attached in some way, shape or form. For example, I write software, and people buy it. They also get the service and support that goes with it. I charge the same price, whether I spend 20 hours on the phone with a customer, or zero hours. It equals out in the long run.
When DJ'ing (or custom programming), I charge an hourly rate of $XXX -- that includes everything I have available at the moment. If it's a simple 4 hour gig (wedding, party, what have you) -- it's 4 x $XXX. The XXX is determined based upon my current market value at the time, and doesn't fluctuate all that much.
I've been doing both for a long time, and I know how to do my job -- if the client feels some odd need to meet with me prior, then they get more XXX's. I work the same way my lawyer and accountants do.
Very simple, and almost all people understand it, and never question it.