Help finding site: shows price mark-ups before black friday?

I think someone posted this site last year but I am pulling from the corners of my mind. I thought there was a site that showed whether or not something is actually on sale on Black Friday/Cyber Monday/etc or if it’s just a dip in price that has been hiked up over the last few months.

Am I making this up or does anyone know what I’m talking about?

88JM19 posted this last November:

Thank you!!!