Payments such as wages or taxes that are calculated on asliding scale are higher or lower depending on various different factors.
Many practitioners have a sliding scale of fees. [+ of]
sliding scale in British English
noun
a variable scale according to which specified wages, tariffs, prices, etc, fluctuate in response to changes in some other factor, standard, or conditions
sliding scale in American English
a standard or schedule, as of costs, wages, fees, tariff rates, etc., that varies in accordance with given conditions or standards, as cost of living, level of income, etc.