I've seen page structure analysis, manually Xpath/CSS selector writing, machine learning, pattern matching, micro-formats, large central databases, etc.
I understand that no company wants to unveil their secrets but this is Hacker News. If you're going to promote your product here at least give us something tech to munch on.
I think using heuristics as mentioned in one of their previous answers might be somewhat novel. But yeah... I worked on a product that did auto-detection of which element was the price on a page at least five years ago. I'd love to learn the differentiators.
[1] https://www.lowes.ca/routers/dewalt-dwp611pk-125-hp-variable...
Our tools (apps and browser extensions) have a 'report' button, so whenever someone encounters an issue, we get notified and we will add it to our 'to fix' list :)