sales pitch; catchphrase
A set phrase used to attract customers or promote a product, often with a persuasive or catchy tone.
That shop's sales pitch is 'The freshness is different.'
I was taken in by his sales pitch and ended up buying it.
More general 'advertising copy' or 'promotional phrase', not necessarily limited to a catchy sales pitch.
Compound of 売り (uri, 'selling') + 文句 (monku, 'phrase' or 'complaint'). The combination yields the meaning of a phrase used for selling.