The cost to become a U.S. citizen depends on several factors. But in general the amount you should pay to process your application for naturalization is $725
us-immigration-knowledge.com.
This amount includes two payments:
A payment for processing the form. This is the filing fee, and it currently equals $640.
A payment for biometric services. The biometric services fee is only $85.
USCIS specifically requires that Form N-400 applicants pay $725 in total. You are also not allowed to pay a smaller or larger amount of money. In other words, pay exactly $725 for your application. If you will pay more than requested, USCIS will deny your application. However, in that case the money you have paid will be returned. Note that USCIS also allows to use credit cards for paying this amount.