Cost of revenues
We had cost of revenues of $3.7 million for the nine months ended September 30, 2024, an increase of $0.1 million or 2%, compared to $3.6 million in the same period in 2023. As a percentage of revenues, cost of revenues was 8% in the first nine months of 2024, compared to 7% in the prior year period.
Engineering and product development expense
We had engineering and product development expense of $3.8 million for the nine months ended September 30, 2024, a decrease of $0.8 million, or 18%, compared to $4.6 million in the same period of the prior year. The decrease was primarily due to lower compensation related and consulting expenses, partially offset by higher clinical studies expenses. As a percentage of revenues, engineering and product development expenses were flat at 9% in the first nine months of 2024, compared to the prior year period.
Sales and marketing expense
We had sales and marketing expense of $10.1 million for the nine months ended September 30, 2024, a decrease of $3.5 million, or 26%, compared to $13.6 million in the same period of the prior year. The decrease was primarily due to lower compensation related expenses, consulting, trade show, travel, and other expenses. As a percentage of revenues, sales and marketing expense decreased to 23% in the first nine months of 2024, as compared to 26% in the prior year period.
General and administrative expense
We had general and administrative expense of $9.0 million for the nine months ended September 30, 2024, a decrease of $2.0 million, or 19%, compared to $11.0 million in the same period of the prior year. The decrease was primarily due to lower compensation related, legal and professional and bad debt expenses, partially offset by higher dues and subscriptions expenses. As a percentage of revenues, general and administrative expense decreased to 20% in the first nine months of 2024, as compared to 21% in the prior year period.
Other (expense) income, net
We had total other expense, net, of $2.1 million, a decrease of $3.6 million for the nine months ended September 30, 2024, compared to total other income, net, of $1.6 million in the same period of the prior year. The change was primarily driven by unrealized loss of $3.9 million from the change in fair value of our digital assets.
Income tax provision
We had income tax provision of $3.6 million for the nine months ended September 30, 2024, a decrease of $1.3 million or 27%, compared to $4.9 million in the prior year period. The effective tax rate for the nine months ended September 30, 2024 was 24%, compared to 23%, in the same period of the prior year. The increase in our effective tax rate was primarily due to the valuation allowance related to net unrealized capital losses incurred due to the change in fair value of our digital assets.
Net income
For the foregoing reasons, we had net income of $11.7 million, or $1.68 per basic share and $1.50 per diluted share, for the nine months ended September 30, 2024, a decrease of $4.7 million, or 29%, compared to a net income of $16.4 million, or $2.44 per basic share and $2.09 per diluted share, for the same period of the prior year.
Liquidity and Capital Resources
We had cash, cash equivalents and restricted cash of $6.7 million at September 30, 2024 compared to $57.3 million at December 31, 2023, and total current liabilities of $6.8 million at September 30, 2024 compared to $6.2 million at December 31, 2023. As of September 30, 2024, we held 1,018 bitcoins with an aggregate fair value of $64.5 million at such date. Our bitcoins are held offline in cold storage with multiple third-party providers. Digital assets like bitcoin depend on private keys to retrieve and transfer funds. A bitcoin is considered an indefinite-lived intangible asset, and our bitcoin investment is remeasured at fair value at each reporting date with changes recognized in net income through “other income (expenses), net” in our condensed statement of