USCIS proposed fee increases in 2020 which would have made significant changes to the prices for many important benefits like citizenship, work permits, and waivers. It also changed policies like allowing people to request a fee waiver based on having low incomes.
On September 29, 2020, a US District Court Judge issued an order stopping the new fee increases from going into effect. On December 28, 2020, the government withdrew an appeal in that same case. It is not expected that the USCIS fee increases will go into effect at this time.
The normal fee for filing an N-400 naturalization application is $725. Some people who have income below a certain level can file for $405. Others with even lower income can file for free. These two lower priced options both require an additional form to be submitted, as well as additional evidence of income. It is recommended to consult with an attorney before filing in those cases to avoid a rejection.