It just made cents.

Major League Baseball star Merrill Kelly will pocket nearly $2.5 million more per year over the next two seasons of his $40 million deal by signing in Arizona instead of California.

The massive difference in cash reflects the spread in state income taxes as well as California’s disability insurance levy and typical property tax differences on a luxury home.

However, the overwhelming driver of the disparity is state income tax.

California’s top marginal rate reaches 13.3% — a 12.3% bracket plus an additional 1% Mental Health Services Tax on income above $1 million. On a $20 million salary, that translates to roughly $2.63 million owed to the state.

Merrill Kelly cited California’s tax burden as a key reason he spurned the San Diego Padres and returned home to the Arizona Diamondbacks. Getty Images

Arizona, by contrast, imposes a flat 2.5% income tax regardless of earnings. On the same $20 million contract, the bill comes to about $500,000.

That difference alone — approximately $2.13 million per year — accounts for nearly all of the gap.

California also withholds 1.3% for State Disability Insurance, with no wage cap. On a $20 million salary, that’s another roughly $260,000 — a levy Arizona does not impose.

Property taxes and sales taxes pale in comparison.

On a $10 million home, California’s effective property tax rate of roughly 0.70% would translate to about $70,000 annually, versus roughly $44,000 in Arizona at an effective rate near 0.44% — a difference of around $26,000 per year.

Kelly will save nearly $2.5 million more annually by signing with Arizona instead of a California club. AP

Even if the home price climbs higher, the property tax gap amounts to tens of thousands

Sales taxes vary by city and spending habits, but they are unlikely to materially alter the overall gap.

For example, if a player spent $1 million annually on taxable goods, a roughly 1 to 1.5 percentage-point difference between jurisdictions would amount to about $10,000 to $15,000 per year.

Even with lavish consumption, the sales tax impact would likely total tens of thousands.

The eye-popping gap came into focus after veteran right-hander Kelly cited California’s tax burden as a key reason he spurned the San Diego Padres and returned home to the Arizona Diamondbacks.

“It’s just, like I said, they take too much money out of my pocket, man,” Kelly said. “The taxes over there are a different level.” IMAGN IMAGES via Reuters Connect

“I don’t think it’s any secret on how much money you get taken out of your pocket when you go to California,” the 37-year-old said.

“It’s just, like I said, they take too much money out of my pocket, man. The taxes over there are a different level.”

After mulling over a potential tax bill, the decision became clear.

“We had my numbers guy run the numbers, and it just made more sense to come home,” Kelly said.

Kelly isn’t the only professional athlete that has been impacted by the taxman in the Golden State.

Seahawks quarterback Sam Darnold will owe California roughly $249,000 in “jock taxes” after winning Super Bowl LX in Santa Clara — about $71,000 more than the $178,000 he earned for the game.

Seahawks quarterback Sam Darnold will owe California roughly $249,000 in “jock taxes” after winning Super Bowl LX in Santa Clara. Getty Images

The bill stems from California’s rule that forces out-of-state athletes to pay state income tax based on the number of “duty days” they work in the state, with Darnold and the Seahawks accumulating eight days during their Super Bowl trip.

The $249,000 California bill was calculated by taking Darnold’s $35 million annual salary, dividing it by his total duty days for the year (roughly 200), then multiplying by the 8 duty days in California, and applying California’s13.3% rate.

If you swap in Arizona’s 2.5% rate with the same formula, Darnold’s bill would have been roughly $47,000 instead of $249,000 — about 80% less. He still would have come out ahead of his $178,000 Super Bowl bonus rather than losing money on it.

So the difference between playing the Super Bowl in California vs. Arizona would have been roughly $200,000 in Darnold’s pocket.