There’s a limit to the number of golden eggs a golden goose will lay. That’s the lesson local taxing entities are in the process of learning.

Riverwalk Casino has filed suit over the $78.1 million value assigned to its casino, hotel and restaurant development that opened in October 2008. The company says its experts looked at the same tax assessment criteria and came up with a value of $30.7 million.

Ameristar, which opened in 1994 and completed its largest expansion to date in 2008, initially got a tax notice valuing its local holdings at $121.7 million and, during a hearing, won a reduction ordered by the Warren County Board of Supervisors to $92.4 million. The company’s experts say that’s still $10 million more than their calculations. They pointed out that the initial valuation based the taxable value of each parking space in the company garage at $37,000 — which is more than the value assigned many homes in Vicksburg and Warren County.

In legal terms, something is terribly amiss when the same state-set appraisal criteria can yield such vastly different valuations.

In financial terms, the impact of casino development on city, county and school treasuries here has been nothing short of game-changing.

Schools here get the short end of revenue taxes, but the largest share of property taxes — about $10 million per year. The county gets millions in revenue and property taxes. Vicksburg proper is the biggest proportional winner, also banking about $10 million — a third of its whole budget — in revenue, property, position fees, bed taxes and sales tax rebates.

The effect of casino revenue here has been profound, to say the least. Only twice in 18 years have local property tax rates been increased — once by supervisors and once by Vicksburg Warren School District trustees. Compare that to neighboring counties without casinos where property tax rates have been increased almost annually, including for the coming year.

Casinos do well here and don’t need any kind of break or discount. Like all the rest of us, however, they need to pay a fair, accurate assessment. That’s what their owners have every right to expect and if it takes a protest to achieve equity, they’re justified in their challenge.