The Gemorah specifically says that when a seller swears he won’t sell for under two, and the buyer swears he won’t pay more than one, the sale may take place for $1.50.
Even though they both are violating their oaths, it was understood that this was just normal mekach u’memchar hyperbole.
This type of advertising seems to fall within the same understanding – it’s understood to be hype, not a factual statement.
(p.s. I don’t recall the actual amounts in the Gemorah)