Ransom, redeem, bought with a price, etc. convey truth, but must be understood in light of word studies, first century culture (vs ours), etc. This is sound hermeneutics and is not a denial of spiritual truths (like sozo and lighthouse jumped to conclusions about 'metaphor').
The payment theory/Commercial Transaction Theory/satisfaction theory originated mostly with Anselm. This confuses metaphor with literal understanding. A religious metaphor conveys spiritual truth, but is not to be taken in a literal, physical way. A literal payment or ransom would logically and legally lead to universalism, which is unbiblical. His death is literal, but the meaning of it is debatable (try the Moral Government view on for size e.g. Albert Barnes; Charles Finney; etc. instead of the Commercial theory).
Caleb Burge, Dr. Nathan Beman, and many others rightly recognize the figure of speech, since a literal understanding of these concepts would contradict more explicit teachings on the nature of redemption. The theological understanding of redemption is also deeper than simply assuming it means a literal payment. Others debated who this supposed payment is made to: Satan, Jesus, Father, man, etc.
Beman: "The Scriptures frequently describe the atonement in language of a figurative character; and the literal construction (interpretation) which has been put upon the language has, no doubt, sometimes...misled the honest inquirer....they do not intend to teach that salvation is a pecuniary transaction, regulated according to the principles of debt and credit...Christ prepared the way for our debt to be remitted...He made it consistent and proper and honorable for sin to be forgiven according to the prescribed terms of the Gospel..." (quote was longer explaining why figurative vs literal debt payment is more biblical)."
Burge: "...figurative expressions..they are designed to communicate the idea, that as payment of money as the price of liberty is the ground on which prisoners are released from captivity, so the atonement of Christ is the ground on which sinners are pardoned, or set free from a sentence of condemnation...understood literally, they would contradict other plain declarations of the Word of God. It is evident, therefore, that these are metaphorical expressions, and were never designed to be taken in a strictly literal sense." (again, longer quote would prove the point).
Salvation did cost something, but it is more than a commercial transaction.
George Otis, Jr. "If we accept the premise that Jesus literally purchased our salvation with His blood, this approach only portrays God as vindictive and bloodthirsty and totally incompatible with biblical forgiveness, it also presents another grave difficulty. If Jesus literally paid for our sins with his blood (a paid debt is no longer a debt),and He died for the sins of the entire world, then we come to only one conclusion, universalism, which means the whole world will be saved. If salvation is basically a legal transaction, then I have no debt or obligation remaining and my ignorance of this situation would not alter the fact." (this is from several chapters of teaching, so do not jump to conclusions out of context)
To try to shore up this error (literal payment), Calvinists revert to limited atonement for the 'elect' (TULIP). The literal payment view is only problematic because many fail to recognize the many metaphors for salvation (cf. , Jesus (door, etc.), the Church (Body), etc.) and press it with a wooden literalism. Recognizing figures of speech avoids contradiction with didactic portions and does not diminish the spiritual truths portrayed by the analogy. Jesus is not a wooden door and salvation is not a mere commercial transaction. This metaphor cannot be divorced from other equally important descriptions of what was and was not accomplished in His death.