One comment in this article is that Aaron earned $240,000 per year and was the best paid player in baseball at his peak salary. Today ARod earns more than that amount in two games. This article is very interesting read.
Here's something more recent. In 1983, Orel Hershiser earned $36,000 in his rookie season. That's probably what A-Rod makes for a single plate appearance. Joe DiMaggio never earned more than $150K for a season. Today, the league minimum is slightly under $200K and most of those guys spend their time ridin' the pine. A salary cap for baseball is a MUST.