Oil me up

I went to the supermarket across the street from my apartment last night to pick up a few neccestities (mostly tissues and pretzels). I had 7 total items, so I got into the Express Lane line, thinking that it would be by far the fastest way out of the store. There were only three people ahead of me, each with no more than the customary 10 items that are allowed in such a lane. To make you fully understand the rest of this story, I will give you a little background on the supermarket itself. It is a fairly large market, especially for NYC, but is populated with the laziest, most uncaring employees I have ever seen collected. LG and I have shopped there many, many times and have rarely met with a cashier who was both competent and nice. All of the people working the cash registers are young women who seem to care more about store gossip and what each other did the night before than doing their jobs. Keeping this in mind, I shall continue with the story...

The first two people in line took about 10 minutes to get rung up. The cashier was talking to someone sitting on a bench behind the row of registers and scanning items at an incredibly slow pace. Finally, she moved on to the guy who was right in front of me. He had 5 items, among them a very large plastic container of vegetable oil. When the cashier rung up the oil it came to 12.99 or something like that.
"Wait a minute," he said "I thought that was on sale for 3.99."
"Nope."
"Are you sure, the guy in the aisle said it was."
"Not this one."
"So which one is it?"
"I don't know."
"Well, could you find out?"
She picks up the weekly flyer and flips through it.
"It's this one," she says, pointing to a picture of Key Food Corn Oil.
"Okay, let me grab it."
He takes off and returns with another large bottle, this time it's Wesson Corn Oil. She takes it from him and rings it up: $7.49.
"This ain't it either."
"What?"
"It's Wesson. You need the Key Food Corn Oil."
"Oh, Canola Oil."
"Yeah, Corn Oil."
He takes off again, but I know he will not bring back the right one. He returns a minute later with another large plastic bottle: Key Foods Canola Oil.
She takes it from him and rings it up: $4.99.
"That's the right one," she says.
"Oh, okay." He gives her a $20, gets his change, and is on his way with the wrong oil at the wrong price. All of that wasted time for nothing. Meanwhile, the rest of the checkout lanes seem to be pretty empty. And there I am, in the Express Lane, just waiting to buy my damn tissues and pretzels. She rings me up, I pay, and I take my bags.

As I walk outside, I think:
Who the hell uses Corn Oil?