The corpus of the trust account shall remain intact until the property or goods are delivered or services performed as specified in the contract: Provided, That the net income from the preneed trust account may be used to pay any appropriate trustee and auditor fees, commissions and costs. The net income from the preneed trust account, after payment of any appropriate trustee and auditor fees, commissions and costs, shall remain in the account and be reinvested and compounded. Any trustee fees, commissions and costs in excess of income shall be paid by the cemetery company and not from the trust. However, the trustee shall, as of the close of the cemetery company's fiscal year, upon the written assurance to the trustee by a certified public accountant employed by the seller, return to the seller any income in the seller's account which, when added to the corpus of the trust account is in excess of the current cost requirements for all undelivered property, goods or services included in the seller's preneed cemetery company contracts including all outstanding preneed cemetery company contracts entered into prior to the first day of July, one thousand nine hundred ninety-three. The seller's cost requirements shall be based upon wholesale cost and certified in its records by a sworn affidavit by the compliance agent and shall be determined by the seller as of the close of the cemetery company's fiscal year.