Cost of Revenue (exclusive of depreciation and amortization shown below)
Cost of revenue increased by $7.1 million, or 37%, from $19.3 million in the three months ended September 30, 2022 to $26.5 million in the three months ended September 30, 2023. The increase was primarily due to growth in our Activation revenue which drove increases in partner costs from revenue-sharing arrangements, as well as accelerated investments in cloud services to provide scale and flexibility necessary to support future growth. Cost of revenue increased by $21.6 million, or 39%, from $55.0 million in the nine months ended September 30, 2022 to $76.6 million in the nine months ended September 30, 2023. The increase was primarily due to growth in our Activation revenue which drove increases in partner costs from revenue-sharing arrangements, as well as accelerated investments in cloud services to provide scale and flexibility necessary to support future growth.
Product Development Expenses
Product development expenses increased by $8.4 million, or 35%, from $23.9 million in the three months ended September 30, 2022 to $32.3 million in the three months ended September 30, 2023. The increase was primarily due to an increase in personnel costs, including stock-based compensation, of $7.1 million, and an increase in third-party software costs and professional fees of $1.2 million primarily to support product development efforts. Product development expenses increased by $24.1 million, or 35%, from $68.7 million in the nine months ended September 30, 2022 to $92.8 million in the nine months ended September 30, 2023. The increase was primarily due to an increase in personnel costs, including stock-based compensation, of $19.4 million, and an increase in third-party software costs and professional fees of $3.5 million primarily to support product development efforts.
Sales, Marketing and Customer Support Expenses
Sales, marketing and customer support expenses increased by $5.9 million, or 22%, from $27.1 million in the three months ended September 30, 2022 to $33.0 million in the three months ended September 30, 2023. The increase was primarily due to an increase in personnel costs, including stock-based compensation and sales commissions, of $4.2 million, an increase in marketing activities, including advertising, promotions, events and other activities of $0.1 million, and an increase in personnel travel and entertainment expenses to support marketing and sales activities of $0.6 million. Sales, marketing and customer support expenses increased by $11.7 million, or 15%, from $78.5 million in the nine months ended September 30, 2022 to $90.2 million in the nine months ended September 30, 2023. The increase was primarily due to an increase in personnel costs, including stock-based compensation and sales commissions, of $8.6 million, an increase in marketing activities, including advertising, promotions, events and other activities of $0.9 million, and an increase in personnel travel and entertainment expenses to support marketing and sales activities of $1.2 million.
General and Administrative Expenses
General and administrative expenses increased by $3.9 million, or 20%, from $19.4 million in the three months ended September 30, 2022 to $23.3 million in the three months ended September 30, 2023. Personnel costs, including stock-based compensation, increased by $2.4 million. In addition, professional services costs related to the acquisition of Scibids were $0.9 million during the three months ended September 30, 2023.
General and administrative expenses increased by $2.6 million, or 4%, from $60.6 million in the nine months ended September 30, 2022 to $63.2 million in the nine months ended September 30, 2023. Personnel costs, including stock-based compensation, increased by $4.6 million. Bad debt expenses increased by $3.3 million, including a reserve established in connection with outstanding amounts owed to the Company by its activation partner, MediaMath Holdings, Inc., which filed for Chapter 11 bankruptcy protection on June 30, 2023. M&A costs increased $0.4 million. Cost increases were offset by a $1.3 million decrease in insurance costs, and a decrease of $4.5 million in other costs that did not recur in the nine months ended September 30, 2023, which include costs related to the departures of the Company’s former Chief Operating Officer and Chief Customer Officer, the impairment of subleased office space and the disposal of furniture for unoccupied lease office space.