Learn English – Does a native speaker say “recharge oneself”

I think we need to clarify a couple of definitions:

• Native English speaker – A person whose first language is English (they learned English from birth or as a very young child), and for whom English is the primary means of communication.

• Fluent English speaker – A person who learned English later in life (i.e. as an older child, teenager, or adult), and who is very proficient in both spoken and written English.

There is nothing wrong with not being a native English speaker, and many non-native speakers have far better English skills than myriads of native speakers.

You can't beat is an idiom meaning "There is nothing better than"; it derives from the use of beat in the sense defeat, prove superior to.

You can't beat bacon and eggs for breakfast.
Whatever you think of the Beatles, you can't beat the Stones for longevity.

In this case, your interlocutor means "There is no better price than free".