business as usual

Every day on my way to school, I pass by a sushi restaurant advertising that their entire menu has a 50% discount every day. The chalkboard outside the restaurant advertises absurdly high markups and then crosses those prices out, showing the "discounted" (read: still overpriced) values.

While this seems like an absolutely ridiculous sales strategy to me, the restaurant is always crowded and I´ve heard people talk about it as a good deal.

I suppose a "good deal" is always relative. For example, it costs half the money to buy an iPod in the states than it does to buy one in Chile. But isn´t it deceptive to use relative price comparison when comparing with completely artificial numbers? Is this business strategy a deceptive manipulation of human psychology?