How dare you give it to me for free!

A few weeks ago I was cashing at my till. There was a bit of a line, but nothing too crazy. I get to a customer whose only item is a pack of toilet paper. I'll call him TP, for short.

Me: "How are you today?"

TP: grumbles

I scan the item, and tell him the total

Me: "That'll be $11.54"

He glares at me

TP (angrily): "The shelf said $8.50"

Me: "Okay I can go check on that for you"

TP: grumbles

I go to the toilet paper, check the price, and the customer is correct, the price is $8.50. My store practices the scanning code of practing, which, for those of you that dont know, means that if the scanned price is higher than the shelf price, the customer gets the item for free, up to $10. I sometimes forget to do it, but I could tell this guy was in a bad mood, so I figured I could try to brighten up his day.

Me: "You were right, it is $8.50"

TP: grumbles

Me: "Your total is $0.85"

Normally we would pay the tax, too, but I already needed two overrides to get to where I am now, and I didn't want to get another. TP just glared at me.

Me: "Since the scanned price was higher than the shelf price, you get the item for free, you just have to pay that tax."

TP: "WHY CAN'T I EVER COME IN THIS STORE AND GET WHAT I WANT AT THE PRICE IT'S ADVERTISED WITHOUT ALL THIS HASSLE?!"

Me: "...are you saying you don't want it for free?"

TP: "NO I DONT WANT IT FOR FREE!"

Me: "Okay...That'll be $8.50"

He paid and left. Most people get extremely excited when I give them something for free (for obvious reasons, who wouldn't like that?!), but this guy was obviously too good for that. Asshole.