I have always understood Romans 6:23 to read "For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus (our Lord)." And that is how my NASB 1995 renders it. But now that I check out the translations and Greek, the picture seems somewhat confused with regard to the inclusion of "free" as an assumed? adjective to "gift".
The translations are divided with the NIV, KJV, and INT not including "free". But then again, the KJV has "free" in Romans 5:15 and 16 and the current NASB has replaced "free" with "gracious" in all 3 instances.
Looking at the Greek, Strongs 5486 charisma, (χάρισμα) is defined as a "a gift of grace, a free gift", but the usage is "a gift of grace, an undeserved favor" . The derivation is said to be Strongs 5483 charizomai (χαρίζομαι) meaning "to show favor, give freely" with usage (a) I show favor to, (b) I pardon, forgive, (c) I show kindness.
My over-all impression then is that the adjective "free" should not be included in any "literal" translations, as appears to have been recognized in the NASB. But I'm no Greek scholar and would appreciate clarification in view of the above confusion. To be clear, I am distinguishing "free" from other terms such as "gracious", due to it's particular meaning and common understanding.