A church is like a business in that it has to pay fixed costs - mortgage, payroll, utilities, insurance, grounds maintenance, cleaning services, cleaning supplies, property maintenance, copier maintenance, office supplies, phone, etc.
It also has to pay for materials used during the service - hymnals, bibles, sheet music, sunday school materials, music supplies (mics, recorded music, etc), piano tuning, A/V equipment and the like.
There is outreach - advertising, community projects, vacation bible school, special Christmas programs and such.
There is inreach - programs designed to help the membership.
Benevolence - direct gifts in money and food to help the community. Churches get a lot of requests in this area and rarely are they refused. People don't know about this because it's done confidentually.
And missionary work. Some of that is spent locally and some of it is spent abroad.
I served on the budget & finance committee at a church I attended prior to moving where I lived now. The pastor made a modest salary, as did the other ministers on the payroll. He paid for his own car & house.
I saw no lavish spending on anything. When they could they had volunteers cutting the grass and cleaning the church to avoid having to pay for those services. I expect most smaller churches operate this way.
The mega-churches have additional resources and are able to take on large-scale ministry projects that maybe smaller churches cannot. Even Prestonworld has a purpose.
There are certainly a few "ministries" where the offerings mostly wind up the pastor's pocket, and that's unfortunate. It is most likely not happening at your local church on the corner.
If you attend a church and have questions about where the offering goes - ask. The budgets are usually available to anyone interested.