To bet (someone) credits to navy beans meant to put up something of high value against an equal number of relatively worthless items. Metaphorically, it indicated one’s strong belief that the statement which followed was true.

A Federation variation on “dollars to doughnuts”, this referred to wagering something of value against something relatively worthless – in other words, “I’ll bet you anything…”

In 2267, DeSalle was willing to bet credits to navy beans that using USS Enterprise’s impulse engines to crash the starship into a force field surrounding them could at least manage to put a dent in it, if not break through it. (TOS: “Catspaw”)

https://memory-alpha.fandom.com/wiki/Economic_parlance

I have to look up basically every English idiom that I come across, so this had not necessarily struck me as odd