Babe Ruth 1921 season salary is around 26 million. How is positional players salary calculated.
John Clarkson 1885 season salary is around 30 million. How is pitchers salary calculated.

the formula for salary calculation is extremely complex and not public but it's based on two main factors: how good the guy is and how many plate appearances (or innings pitched for a pitcher) he had. so if you have two pitchers of similar effectiveness, and one pitched 150 innings and the other 300 innings, the 300 inning pitcher will be twice as expensive. same logic for hitters.

there was also a brief experiment in dynamic pricing that led to many players having their salary adjusted from the baseline. the main effect of this was the very best players saw their salary go up by a lot, and some players who were perceived as being undervalued and thus used frequently also saw big increases.

Mostly, it makes 2016+ (or thereabouts) players are a better value than the oldies. Well, all things being equal that is, which they're not. My opinion, as 06 put it in a gentle way, is that the way salaries are constructed, and are also warped by "normalization" and where playing time eligibility is way overvalued. The new owners' know these faults, and are working on a complete rebuild. (Lets hope anyway.)