In 1991 the Legislature enacted the Childhood Lead Poisoning Prevention Act to provide evaluation, screening, and follow-up services for children who were at risk of suffering lead poisoning. The program of screening and treatment under the act was to be paid entirely by fees paid by those who contributed to lead contamination. In Sinclair Paint Co. v. State Bd. of Equalization (1997), the Supreme Court concluded the act imposed bona fide regulatory fees, not taxes. Sinclair is the first published case in the post-Proposition 13 era to consider whether a state, rather than a local, fee is in legal effect a tax. "Section 3 of article XIII a restricts the enactment of changes in state taxes, as follows: 'From and after the effective date of this article, any changes in State taxes enacted for the purpose of increasing revenues collected pursuant thereto whether by increased rates or changes in methods of computation must be imposed by an Act passed by not less than two-thirds of all members . . . of the Legislature, except that no new ad valorem taxes on real property, or sales or transaction taxes on the sales of real property may be imposed. ' " (Sinclair Paint Co. v. State Bd. of Equalization, supra, 15 Cal. 4th at pp. 872-873.) By contrast, there have been an abundance of cases in which courts have struggled to characterize a local exaction as a fee or a "special tax" under California Constitution, article XIII A, section 4. In Sinclair, the Supreme Court announced that "because of the close, 'interlocking' relationship between the various sections of article XIII A" the section 4 cases "may be helpful, though not conclusive" in deciding cases under section 3. (15 Cal. 4th at p. 873.) The court also reiterated the fundamental principle that "whether impositions are 'taxes' or 'fees' is a question of law for the appellate courts to decide on independent review of the facts." (Sinclair Paint Co. v. State Bd. of Equalization, supra, 15 Cal. 4th at p. 874.) Ordinarily, "taxes are imposed for revenue purposes, rather than in return for a specific benefit conferred or privilege granted" and "most taxes are compulsory rather than imposed in response to a voluntary decision to develop or to seek other government benefits or privileges." ( Id. at pp. 873-874, 64 Cal. Rptr. 2d 447, 937 P.2d 1350.) Sinclair was particularly helpful in identifying three very different kinds of fees or assessments, viz. special assessments, development fees and regulatory fees. (See also Isaac v. City of Los Angeles (1998) 66 Cal. App. 4th 586, 596 [77 Cal. Rptr. 2d 752].) As the court pointed out, special assessments are based on the value of benefits conferred on property, and development fees are exacted in return for permits or other government privileges. Regulatory fees, enacted under the police power, are an entirely different animal. The parties have failed to distinguish between these types of fees and, consequently, have extracted general principles from cases involving one type of fee and applied them to cases involving a completely different type of fee. Fees charged for the associated costs of regulatory activities are not special taxes under an article XIII A, section 4 analysis if the "fees do not exceed the reasonable cost of providing services necessary to the activity for which the fee is charged and [they] are not levied for unrelated revenue purposes." (Sinclair Paint Co. v. State Bd. of Equalization, supra, 15 Cal. 4th at p. 876; Townzen v. County of El Dorado (1998) 64 Cal. App. 4th 1350, 1359 [76 Cal. Rptr. 2d 281].) "A regulatory fee may be imposed under the police power when the fee constitutes an amount necessary to carry out the purposes and provisions of the regulation." (San Diego Gas & Electric Co. v. San Diego County Air Pollution Control Dist. (1988) 203 Cal. App. 3d 1132, 1146, fn. 18 [250 Cal. Rptr. 420].) "Such costs . . . include all those incident to the issuance of the license or permit, investigation, inspection, administration, maintenance of a system of supervision and enforcement." (United Business Com. v. City of San Diego (1979) 91 Cal. App. 3d 156, 165 [154 Cal. Rptr. 263].) Regulatory fees are valid despite the absence of any perceived "benefit" accruing to the fee payers. ( Pennell v. City of San Jose (1986) 42 Cal. 3d 365, 375 [228 Cal. Rptr. 726, 721 P.2d 1111], affd. on other grounds sub nom. Pennell v. City of San Jose (1988) 485 U.S. 1 [108 S. Ct. 849, 99 L. Ed. 2d 1].) Legislators "need only apply sound judgment and consider 'probabilities according to the best honest viewpoint of informed officials' in determining the amount of the regulatory fee." ( United Business Com. v. City of San Diego, supra, 91 Cal. App. 3d at p. 166.)