Fucking AnazonBasics pulled this shit with something I bought. Not quite as bad; it was still technically on sale, but only by $2 instead of the $7 they would have you believe.
Yea, I don't assume anything is on sale until I've looked at camelcamelcamel.com. Even then, it doesn't get lightning deals, and some other random promotions, so it can be difficult to tell what an actual good price is.
Camelcamelcamel is good, but Keepa has a browser extension that shows the price graph directly on the Amazon page, so you don't have to go anywhere or click anything to see it.