Easter Eggs - Eggsactly Puzzle

This is Hungry Horace's favourite type of Easter Egg.

He went to the shop to buy one but found that the Easter Eggs had been packed up in boxes of three like this:



"How much does this one egg cost?" Horace asked the shopkeeper.

"That's easy", he replied "It's just ....."

Then the telephone rang and he had to answer it.

HOW MUCH DOES HORACE'S FAVOURITE EGG COST?