Actually, Andrew, it is an error of biblical interpretation to assume that the context of meaning of a word is divorced from its social and cultural context. You have produced no evidence for what you assert - that paid in full was not at least one way in which the word would have been understood by 1st century readers. Very many people seem to disagree with you.

Further, very many people seem to disagree with you that tetelestai had no particular emphasis. Even if it meant simply It is finished, and did not carry any of the other overtones which are quite validly associated with the word, we would still probably be discussing whether it meant something beyond my physical life is finished - at one end of the spectrum, and my atoning sacrifice has been made at the other. This is because, as I mentioned elsewhere, the final words of Jesus are not just the final of words of any ordinary individual, but, at the least, of a very special individual indeed. Careful attention was likely to have been paid to what he said at his death. Further, his final words would have been understood in the light of his life as whole - not just as fragementary utterances with no connection to earlier sayings, or things said about him, or the broader narrative which he was acting out (see below).

Also, Just to add that the word used in John19:28 is not tetelestai, (though it’s from the same verb), and there are only two uses of this form of the verb in the NT. You have not proved anything by citing the connection between Psalm 69 and John 19:29 (in the first place) and John19:30 (in the second place). The narrative suggests to me just as powerfully that Jesus was suffering the suffering of the righteous in Israel’s history, but with a redemptive significance. This is brought out in the use of tetelestai (whether it has commercial redemptive significance or not), because it must be interpreted in the light of Jesus’s life as a whole - not least as presented in John’s gospel.

Leaving aside the use of redemption imagery on scores of occasions in Israel’s history in the OT, and in Jesus’s death on many occasions in the NT, the death of Jesus on the cross, and therefore in the whole of John 19, brings out the theme in a particular way. The greatest image of redemption in Israel’s story was the Passover, leading to release from slavery in Egypt, and ultimately entry into the promised land. When John makes this association with Jesus in John 1:29, the only place where it could have been fulfilled was in Jesus’s death on the cross - the place where the Passover lamb was slaughtered. Tetelestai is therefore also to be interpreted in the light of this narrative. There is no conflict at all between this narrative and the narrative of Psalm 69 - which Jesus invokes on the cross. The former narrative is, actually, the dominant narrative. It was at the Passover that Jesus was killed. Psalm 69 fits within that narrative as describing, for Jesus, the suffering he must undergo to fulfil the Passover narrative.

I may have exaggerated things in my complaint about redemption imagery
not being considered. You do of course consider it - actually, it’s at
the heart of what you have to say about John 19:29-30. What you do not
wish to consider is that redemption imagery had to do with anything
outside Israel and her history. That’s where we fundamentally differ. But I sometimes wonder if we are arguing over words, rather than meanings or significances. It’s important to you to assert that Israel’s narrative was her narrative, and not intended for universal significance. But actually, the promise to Abraham was of universal significance - it was a promise of blessing to the whole world, and a promise that Abraham’s descendants would fill the whole earth. Who were Abraham’s descendants? Those who appropriated the promise by faith. Were these only strictly those who were part of the original narrative, and believing Israel in the first century who survived calamity? Of course not. So for whom was the atoning death of Jesus intended? For Israel within her narrative? Certainly. But for the descendants of Israel, who would fill the whole earth, and who were not simply those who were part of the original narrative? Of course - it was for them as well, as was proved when the gospel of the death and resurrection of Jesus was preached to them, and they received the Spirit.

I don’t wish to suggest there are no differences between us, but I do think you have not really provided a satisfactory explanation of events and developments in history, foreseen in the scriptures, which make a universal atonement of Jesus an unavoidable conclusion and reality.