Is the teaching about the death of Christ in 1 Timothy 2:6 – “a ransom for all” – significantly different than Mark 10:45 – “a ransom for many”?
No, the two passages are not teaching different implications of Christ’s death. Unfortunately, what has sometimes been taught is that the different Greek prepositions, both translated as “for,” necessitate a vastly different interpretation. In Mark 10, the Greek preposition is “anti” and in 1 Timothy 2 the preposition is “huper.” It has been said that “anti” in Mark 10 means “instead of,” but “huper” in 1 Timothy 2 means “on behalf of”; thus Christ’s ransoming work was on behalf of all (1Ti 2), but He was only a substitute in the stead of a smaller subset of mankind (the “many” of Mark 10). That explanation errs on four accounts.
The context of 1 Timothy 2:1-7 is emphasizing “all” (all people in v1, all who are in high positions of government in v2, God desires to save all people in v4, and Christ gave Himself a ransom for all in v6). There is nothing in the context to make us think we are meant to limit the effect of Christ’s ransom in comparison to other passages, such as Mark 10. The context stresses all people.
While “many” is certainly sometimes intended as a contrast to “all,” particularly in Greek contexts, it can be argued that in Jewish contexts (such as the Lord’s words in Mark 10), “many” is in contrast to “one” and bears an inclusive meaning akin to “all.” It is doubtful that Mark 10 is embracing anyone less than the “all” of 1 Timothy 2.
While some are keen to point out the different prepositions (anti in Mark 10, huper in 1 Timothy 2) and seek to build a mountain of theological significance out of it, they tend to overlook that the passages use different words for “ransom.” In the gospels the word is “lutron”; in 1 Timothy the word is “antilutron.” Notice that the preposition “anti,” conveying substitution, is now attached to the word for “ransom.” In other words, Christ gave Himself as a substitutionary ransom for all.
While Greek prepositions obviously have meanings, they have various shades of meaning and can be used in different ways. When Paul speaks of Christ’s death in his writings he doesn’t use “anti” but uses “huper,” which has a broader semantic range and often includes the concept of substitution. The context in 1 Timothy 2 and its linguistic links to Mark 10 show that substitution is in mind in 1 Timothy 2.
The words of 1 Timothy 2 (“huper all”) reflect a reworking and restating of Mark 10 (“anti many”). They are equivalent statements and the two passages parallel one another in their meaning.
 Joachim Jeremias, TDNT VI, pp.536 ff.
 There is abundant support for this, e.g., J.H. Thayer’s Greek-English Lexicon, R.C. Trench’s Synonyms of the New Testament, A.T. Robertson’s New Testament Word Pictures, but especially Murray J. Harris’ Prepositions and Theology in the Greek New Testament.