Economic insanity at the grocery store

Today I walked into the Giant grocery store across the street from my apartment to buy some strawberries. But something struck me as strange: while one pound of strawberries cost $2.99, the two pound package cost a whopping $6.99—more than twice as much!

Never in my life have I seen a business charging you MORE to buy more of its product. Either Giant has stumbled upon some economic law (or magic) that can somehow justify a volume markup (in which case it’s time to buy up Giant’s stock), or Giant's shoppers are extraordinarily bad at math—and the store is only too happy to part them from their cash.

UPDATE- A friend alerted me to a third possibility: this could make an excellent arbitrage opportunity. Find a bunch of empty two pound baskets, buy up all the one-pounders, load the strawberries into the two-pound baskets, and return them to the store, enjoying the $1 per basket profit. Of course, the obvious issues here are (1) Giant doesn't take returns of fresh fruit, and (2) they'd see the one-pound packages on the receipt and know what I was up to. Nevertheless, it's a good quality to have: a nose trained to sniff out arbitrage opportunities will lead one day to riches.