"אָח לֹא־פָדֹה יִפְדֶּה אִישׁ לֹא־יִתֵּן לֵאלֹהִים כָּפְרוֹ׃
וְיֵקַר פִּדְיוֹן נַפְשָׁם וְחָדַל לְעוֹלָם׃
וִיחִי־עוֹד לָנֶצַח לֹא יִרְאֶה הַשָּׁחַת׃ "
teaches that (all the) wealth and riches (from this world) cannot redeem a man, nor pay his ransom to G-d. This is because the redemption of the soul is too costly/expensive; the price for life is too high... [and so one would cease to be, forever].
A couple of verses later David makes the claim (verse 16) that G-d will redeem his life:
"אַךְ־אֱלֹהִים יִפְדֶּה נַפְשִׁי מִיַּד־שְׁאוֹל כִּי יִקָּחֵנִי סֶלָה׃ "
So how does G-d pay this ransom and redeem his soul? Or does He just write-off/cancel the debt ?