Why did it cost me twenty seven dollars for fifteen pounds of Cortland apple's ??

...Because apples aren't free unless you grow them in your own backyard. A bag of apples at the grocery store is $5 for 2 pounds...or $2.50/lb. You are technically getting a discount by picking your own.

It's not how many apples it's how much each weights

Because Cortlands are $1.80 a pound. I payed $2 per pound for the honey crisp, we picked up 15 pounds of them yesterday.