Tall rant

This lady came in and walks up to the register, wearing a Louis Vuitton face-mask. She doesn’t say a word to me and just shoved her phone up to the glass. There was a picture of a drink (it was a venti strawberry açaí refresher with no water and 3 scoops of each fruit, minus kiwi) and so I typed it in for her. She then yells at me that she wants a Trenta—-okay no problem. I type in the total and tell her it’s going to be $6.45. She starts yelling at me that it’s always $5.91 and why is it so much more expensive. I explain to her that since she is getting a bigger size it is more expensive. She’s angry and huffs and puffs as she pulls out her GUCCI wallet. She pays for her drink and then leaves.
Why are people like this? I don’t make the prices.