Cost of sales (excluding depreciation, depletion and accretion) related to product revenue decreased by $1.9 million to $66.1 million for the three months ended June 30, 2025, as compared to $68.0 million for the three months ended June 30, 2024. This decrease was due to higher costs related to the temporary loadout equipment associated with the mechanical fire at the Kermit facility for the three months ended June 30, 2024.
Cost of sales (excluding depreciation, depletion and accretion expense) related to services decreased by $10.2 million to $123.9 million for the three months ended June 30, 2025, as compared to $134.1 million for the three months ended June 30, 2024. The decrease was due to lower freight costs associated with higher utilization of the Dune Express.
Cost of sales (excluding depreciation, depletion, and accretion expense) related to rentals is $5.9 million for the three months ended June 30, 2025, due to the acquisition of Moser and the cost of sales associated with leasing power equipment. There was no cost of sales related to rentals for the three months ended June 30, 2024.
Depreciation, depletion and accretion expense. Depreciation, depletion and accretion expense increased by $15.6 million to $40.6 million for the three months ended June 30, 2025, as compared to $25.0 million for the three months ended June 30, 2024, due to additional depreciable assets placed into service when compared to the prior period as well as contribution from Moser.
Selling, general and administrative expense. Selling, general and administrative expense increased by $7.1 million to $34.4 million for the three months ended June 30, 2025, as compared to $27.3 million for the three months ended June 30, 2024. The increase is due to an increase of $2.8 million from stock-based compensation, an increase of $0.2 million in corporate costs, as well as $4.1 million contribution from Moser for the three months ended June 30, 2025, compared to the three months ended June 30, 2024.
Our selling, general and administrative expense includes the non-cash expense for stock-based compensation expense for equity awards granted to our employees. For the three months ended June 30, 2025, stock-based compensation expense was $8.3 million, as compared to $5.5 million of stock-based expense for the three months ended June 30, 2024.
Credit loss expense. Credit loss expense is $4.1 million for the three months ended June 30, 2025, as compared to no credit loss expense for the three months ended June 30, 2024, due to certain shortfall receivables. See Note 2 - Summary of Significant Accounting Policies - Accounts Receivable and Allowance for Credit Losses for more information.
Amortization expense of acquired intangible assets. Amortization expense of acquired intangible assets increased $2.7 million to $6.5 million for the three month ended June 30, 2025, as compared to $3.8 million for the three month ended June 30, 2024. The increase was primarily due to the amortization of intangibles associated with the Moser acquisition.
Loss on disposal of assets. There was no loss on disposal of assets for the three months ended June 30, 2025, as compared to $11.1 million loss on disposal of assets for the three months ended June 30, 2024, due to $11.1 million disposal of certain assets associated with mechanical fire at the Kermit facility. See Note 6 - Property, Plant and Equipment, Net - Impairment or Disposal of Long-Lived Assets for more information.
Insurance recovery (gain). There was no insurance recovery for the three months ended June 30, 2025, as compared to $10.0 million insurance recovery for the three months ended June 30, 2024, due to $10.0 million of an insurance claim associated with the mechanical fire. See Note 6 - Property, Plant and Equipment, Net - Impairment or Disposal of Long-Lived Assets for more information.
Interest (expense), net. Interest expense, net increased by $4.3 million to $14.8 million for the three months ended June 30, 2025, as compared to $10.5 million for the three months ended June 30, 2024. The increase is driven by the 2025 Term Loan Credit Facility and associated debt refinancing.
Income tax expense (benefit). Income tax expense (benefit) decreased $4.8 million to $(1.7) million for the three months ended June 30, 2025, as compared to $3.1 million for the three months ended June 30, 2024. The decrease is primarily attributable to a decrease in income before income taxes for the three months ended June 30, 2025 as compared to the three months ended June 30, 2024.
Six Months Ended June 30, 2025 Compared to Six Months Ended June 30, 2024
Product Revenue. Product revenue increased by $24.4 million to $266.0 million for the six months ended June 30, 2025, as compared to $241.6 million for the six months ended June 30, 2024. An increase in sales volume contributed to a $61.0 million increase in product revenue. This was partially offset by a decrease in proppant prices between the periods which contributed to a $60.5 million decrease in product revenue. There was $23.9 million in shortfall revenue for the six months ended June 30, 2025, as compared to no shortfall revenue for the six months ended June 30, 2024.
Service Revenue. Services revenue, which includes freight for last-mile logistics services, increased by $58.5 million to $297.0 million for the six months ended June 30, 2025, as compared to $238.5 million for the six months ended June 30, 2024. The increase in logistics revenue was due to higher sales volumes shipped to last-mile logistics customers.
Rental Revenue. Rental revenue is $23.3 million for the six months ended June 30, 2025, due to the acquisition of Moser and the related revenue from leasing power equipment. There was no rental revenue for the six months ended June 30, 2024.