General:
* Buyer
* Purchaser
* Customer
* Patron
* Client
* User
* End-user
More specific:
* Shopper (emphasizes the act of buying)
* Subscriber (for services like streaming)
* Reader (for books, magazines, etc.)
* Viewer (for television, movies, etc.)
* Listener (for radio, podcasts, etc.)
* Audience (for events or media)
* Target market (in a business context)
* End-customer (in a supply chain context)
Formal:
* Ultimate consumer
* End-user
Informal:
* Folks
* People
* The public
The best synonym will depend on the specific context of your writing.