Tacos Los Magueyes

Second time in a week I tried a place where they charge more than the menu prices.
This time a lot more!!!
I ordered a Number 5 Combo Una Enchilada Y Taco, there was no price on the menu board, but the takeout menu she handed me said $ 4.25. I ordered a medium Diet Coke. The menu board at the ordering counter said it was 1.50. That comes to 5.75 and just as I get a call, I hand her a ten dollar bill, and it doesn’t register that she said «8.33». I get my change and as I am waiting for the order, it dawns on me that 5.75 and 8.33 aren’t even remotely close.
I asked her about it, and she explains it’s plus tax, I point out that the tax on 5.75 is less than 57 cents, not the $ 2.54 she overcharged me.
She explains that the price of the drinks went up and points to a DIFFERENT sign that contradicts the sign I saw.
I pointed out that that is a 50 cent difference, how did it get to be a 2.58 discrepancy?
She tells me that she gave me an old take-​out menu they don’t have one with the current prices. I ask her to adjust the prices. she refuses. i ask for my money back, she complies.
She actually gives me 9 dollars back, rather than the 8.33 I paid her. And even though I normally don’t let a cashier make an error in my favor, this time I don’t point it out, Meanwhile the cook finishes what would have been my order. It was probably wasted.
6:15 pm on a weekday. I was the only customer at dinner time, and they lost money on me,.
Go figure.