The city of Lewiston has about 2 voters for every 1 voter in the city of Auburn. The taxable valuation in both cities is nearly equal. Taxes are assessed by multiplying the mil rate by the taxable valuation, less certain exemptions such as homestead exemptions. This means, in a merged city, the people from the Auburn side of the river will pay property taxes about equal to the people on the Lewiston side of the river. (Lewiston taxpayers will pay a higher mil rate to pay down whatever debt they have piled up, as will Auburn's, but to a lesser extent because the debt is lower in Auburn)
So, Auburn's population of 23,000 will pay an equal amount of property taxes as Lewiston's 36,000. Such a deal for Auburn this merger is! Not.