I'd like to ruin gwern's sale too, but my misspent youth as a philosophy major just came back to haunt me.

[EDIT: This paragraph is completely wrong; see below. The end of 1 Corin 6:19 does not say "you are not your own"; it literally says "and [it] is not your own" (= καὶ οὐκ ἐστε ἑαυτῶν) with an omitted subject. The only real possibility is the subject of the previous phrase, which you rendered as "your members." (= τὸ σῶμα ὑμῶν) I find this problematic (and not "clearly stated"), because σῶμα means both the Church as a group (usually in the form, "the body of Christ") and the physical body, as it does in e.g. Mat 10:28: "Do not be afraid of those who kill the body but cannot kill the soul. Rather, be afraid of the One who can destroy both soul and body in hell."]

Since in context 1 Corin 6:12-20 is about sexual immorality, I find the latter interpretation more compelling.

Regarding the Catholic tradition, time was when the Church claimed the authority to discharge sin from the soul in exchange for money.