I run a cap in my fictional league. I started in 1931 and simmed ahead to 1972 to get some history. I then started a cap at $10 million in 1972, I'm now in 1990 and my cap is at $15.4 million. To set average salaries for players, I just googled the actual minimum salary of that year and started there - it was $13,500 in 1972. Whenever I let my cap go up, I added the percentage it went up to my minimum salary. Currently my minimum salary is $36,500, which is actually off the minimum salary of that year (1990), which was $100,000. You can get the minimum salaries here:
https://www.baseball-almanac.com/cha...salaries.shtml