Anyone who provides a service and says there are no expenses is either a liar, an idiot, or just not taking their business seriously. Even prostitutes have expenses.
For the DJ: Music, Equipment Upkeep, Insurance, Advertising, Vehicle Maintenance, Office Supplies... these are all expenses associated with every event you perform at. Add them up.
Balogny, DJ service is easily rendered without incurring much if any of the expenses you cite. Your model is very much out of date. This little corner of the world doesn't work that way anymore. Very few DJs need to operate according to your expensive business model - and the customers are very much aware of that fact!
Music - I spend more on shipping fees.
Equipment - Cheap and easily manageable, assignable, or outsourced.
Insurance - Less than an internet connection for general liability covering a Disc Jockey
Vehicle - I would still own a vehicle and with the added tax deductions it's not a big additional expense.
Phone/internet - You'd still have both even if you weren't a DJ - now you get a tax break.
Office - Home office saves - with deductions and depreciation. U.S. Treasury effectively picks up 7% of my cost, plus a deduction for depreciation.
Advertising - matter of ability & resources, can do a lot of effective outreach with little or no money.
Stop operating like a museum or showcase. You are not a collector - you're a DJ. There is always a high cost associated with buying, storing, and moving things around. If your model is a gear & music collector - someone (consuming) managing and moving inventory rather than selling a unique independent skill/labor then you are wasting money and time on non-unique inventory. (There are more than enough LED lights and speakers to go around.) If you have a core resource that is your knowledge and indispensable skills then much of the expense you cite is unnecessary.
The majority of DJs are part-time players, not business entities. That is not a fault or problem - it is a reality of the endeavor that it is economically best served from a very small plate.
The problem occurs where people take on DJ or other responsibilities when they already lack the resources to do so. If a person has to spend $400 on new tires - that is not a DJ expense. It is a living expense and the fact that they got a flat while at a gig doesn't alter that reality. It also makes no sense to solicit occasional baking jobs if the first one you book requires you to buy an oven.
Work with what you already have. Rent/Lease when the demands depart from that list - and buy only when confirmed work will pay in full for the purchases. Do not buy things on the "hope" or expectation that future (non-existent) jobs will pay for something.