An example of a non-exchange revenue is

Non-exchange revenues are those in which a government gives or receives value without directly receiving or giving equal value in return. Sales taxes are a classic example of a non-exchange revenue because the payer (consumer) does not receive a direct, measurable benefit from the government in exchange for the tax paid.

Other examples of non-exchange revenues include property taxes, grants, and fines. In contrast, licensing fees and investment earnings are exchange or exchange-like revenues, since they involve a mutual benefit or earnings return.

Relevant Standards and References:

GASB Statement No. 33, Accounting and Financial Reporting for Nonexchange Transactions

GASB Codification Section N50

GFOA Revenue Classification Guidelines