I’M a sucker for a sale, the kind of shopper who tallies the amount “saved” rather than spent. My arithmetic goes like this: It makes more sense to buy the $125 cashmere sweater marked down to $95 than to pay full price for the $80 one.

Following this logic, when I heard on the radio that lobster prices were the cheapest they had been in 25 years, I decided that the sensible thing to do was to run over to the fish store and buy a couple for dinner.

So what if I spent nearly $30 on lobster for two on a weeknight when we weren’t celebrating anything? It cost a third less than it would have last year.

While fantasizing about ways to cook my bargain crustaceans, I asked Lewis Spada, the manager of Fish Tales in Brooklyn, why prices were so low.