Vehicle leasing revenue decreased by $430, or 9%, from $4,559 for the three months ended September 30, 2022, to $4,129 for the three months ended September 30, 2023 and decreased by $871, or 7%, from $12,493 for the nine months ended September 30, 2022, to $11,622 for the nine months ended September 30, 2023. Overall, vehicle leasing revenue remained relatively consistent during the three and nine months ended September 30, 2023, and 2022 as sales of vehicles with repurchase obligations continues to represent a small portion of overall sales volumes.
Other revenue increased by $9,829, or 1005%, from $978 for the three months ended September 30, 2022, to $10,807 for the three months ended September 30, 2023. The increase was primarily driven by a sale of intellectual property of $4,340 to a related party, as well as sales-based royalties received from Volvo Cars on sales of parts and accessories and sales of parts and accessories to dealers in the United States and Canada. Other revenue increased by $19,776, or 370%, from $5,349 for the nine months ended September 30, 2022 to $25,125 for the nine months ended September 30, 2023. The increase was similarly due to sales-based royalties and sale of intellectual property. In general, higher revenue on parts and accessories is correlated with higher sales volumes of the Polestar 2.
Cost of sales and gross profit
Cost of sales increased by $178,191, or 41%, from $431,390 for the three months ended September 30, 2022 to $609,581 for the three months ended September 30, 2023. Cost of sales increased by $403,963, or 28%, from $1,419,271 for the nine months ended September 30, 2022 to $1,823,234 for the nine months ended September 30, 2023. These increases were driven primarily by expanded production and commercialization of the Polestar 2 leading to higher contract manufacturing and warranty costs, unfavorable powertrain mix from the long-range single motor powertrain and inventory impairment. This was partially offset by positive impacts from foreign currency effects.
Gross profit decreased by $458, or 11%, from $4,059 for the three months ended September 30, 2022 to $3,601 for the three months ended September 30, 2023. The decrease was primarily driven by an irregular supplier charge related to semiconductors of $4,914, and inventory impairment of $27,620, offset primarily by $35,076 from positive foreign currency impacts on contract manufacturing costs.
Gross profit decreased by $36,262, or 63%, from $57,475 for the nine months ended September 30, 2022 to $21,213 for the nine months ended September 30, 2023. The decrease was primarily due to higher contract manufacturing, warranty, and freight costs of $57,198, irregular supplier charges related to batteries and semiconductors of $22,528, and inventory impairment of $39,415. These unfavorable impacts were offset primarily by $26,755 from price increases established in the second half of 2022, net of higher discounts during the nine months ended September 30, 2023, $43,389 from foreign currency transaction effects on contract manufacturing costs. Overall, the GBP, EUR, and USD have continued to strengthen against the SEK and CNY, resulting in positive impacts to cost of sales and gross profit.
Selling, general, and administrative expense
Selling, general, and administrative expense increased by $57,603, or 32%, from $178,643 for the three months ended September 30, 2022, to $236,246 for the three months ended September 30, 2023. The increase was primarily due to higher advertising, selling, and promotional activities of $46,411 related to media campaigns across European markets during the three months ended September 30, 2023. The Group also incurred higher administrative and selling personnel expenses of $6,583 during the three months ended September 30, 2023, primarily related to costs incurred to meet demands of the growing business.
Selling, general, and administrative expense increased by $59,453, or 10%, from $625,424 for the nine months ended September 30, 2022 to $684,877 for the nine months ended September 30, 2023. The increase was primarily due to higher advertising, selling, and promotional activities of $50,875 primarily related to media campaigns across European markets, Polestar promotional events in the United States and Asia, and marketing productions for the Polestar 3 and 4 during the nine months ended September 30, 2023.
Research and development expense
Research and development expense increased by $30,267, or 123%, from $24,598 for the three months ended September 30, 2022, to $54,865 for the three months ended September 30, 2023. Research and development expense increased by $12,823, or 10%, from $123,353 for the nine months ended September 30, 2022 to $136,176 for the nine months ended September 30, 2023. These increases are driven primarily by an increase in headcount costs for full-time employees combined with derecognition of previously capitalized costs related to a change in electrical architecture for Polestar 5 during the three months ended September 30, 2023. These increases are partially offset by lower amortization of intellectual property related to the Polestar 2 following a revision in the estimated useful life and recognition of sunk costs related to the P10 powertrain, which were incurred in March and June 2022.
Other operating income (expense), net
Other operating income (expense), net increased by $23,524, or 846%, from $2,781 for the three months ended September 30, 2022 to $26,305 for the three months ended September 30, 2023. Other operating income (expense), net increased by $82,847, or 461% from an expense of $17,961 for the nine months ended September 30, 2022, to an income of $64,886 for the nine months ended September 30, 2023. The changes for the three and nine months ended September 30, 2023 were primarily driven by positive foreign exchange effects on working capital and a recognition of a gain on the sale of the Chengdu manufacturing plant of $16,467 during the three months ended September 30, 2023.
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