I had the exact same thing with a D&D book. I don't remember which (it was 5th ed, so fairly recent), but online it was equal to the Amazon price. In person it was like $10-20 more, and yeah, wouldn't price match.

Taught me to never look at B&N for a book I wanted again. I only ever go in there now when I happen to pass one with time to kill and just want to browse.