Their blog[0] has some info. There was a great Software Engineering Daily podcast about it [1] - specifically they use the Amazon Advertising API (still) although the nature of their relationship has changed over the eleven years. I imagine the affiliate rates drastically dropping during Covid, hurt them a fair bit.

[0]: https://camelcamelcamel.com/blog/how-our-price-checking-syst... [1]: https://softwareengineeringdaily.com/2019/05/24/camelcamelca...