The Luxury Tax
Baseball has no salary cap. It has a tax on payroll above a threshold, and clubs treat it like a cap anyway.
What it actually is. There is no salary cap in Major League Baseball. Instead there is a Competitive Balance Tax: a club whose payroll exceeds a threshold pays a percentage on the excess, rising with each consecutive year over it and with each additional tier. Payroll is calculated using the average annual value of contracts rather than the money actually paid that year.
What somebody who knows the game gets out of it. The average annual value rule is why long contracts exist in the shape they do. A ten year contract at 30 million a year counts as 30 million against the tax every year, including the last ones when the player is 38 and not worth it, so clubs deliberately extend contract length to lower the annual number. That is a tax rule shaping player careers, and it is the reason so many deals now run past a player's likely useful life.
The numbers worth knowing. The threshold has run in the low 200 millions and rises each year of the agreement. Penalties escalate through multiple tiers, and repeat offenders pay higher rates and lose draft position.
What people get wrong about it. Most clubs treat the first threshold as a hard cap even though it is not one, which is the criticizm the players' association makes of the whole structure. The tax is a soft constraint that behaves like a hard one because owners choose to treat it that way.
At Little League and travel ball. No equivalent, though travel baseball has its own money question, which is what a season actually costs a family in fees, travel and equipment. The travel section covers fees and what they buy by sanction.
Batter's Eye: look up anything in baseball