You say the quality of the food was the same, as 8 years ago, but the cost of the food, fuel to cook it and staff to do so and deliver it are vastly increased from 8 years ago. But you're expecting better quality than 8 years ago because you're paying more. You're not paying more because they've increased their prices in order to increase the quality, you're paying more because the cost to deliver that same burger and curry to the same standard today is higher than it was 8 years ago.
No, I'm not expecting better quality. That's my point. I'm perfectly happy with my £15 burger and curry at the same quality as I was getting 8 years ago. Because as you say, I accept fully that the cost of making that food has gone up substantially. And that's probably why this restaurant is the local I go to the most often - yes, the price has gone up, but I haven't noticed any deterioration in quality.
My problem, is that lot of other places have also put up their prices, often MORE substantially, but the quality has simultaneously decreased. My local pub was never cheap, but it did used to be reliable and the food was fine. Now, I'm expected to pay £18 for a burger that at least half the time is over cooked and dry.
There do seem to be a lot of places that are using increased costs as an excuse to further increase their prices, without maintaining their quality and it's something I see a lot.
Perhaps another way to put it is that as a rule, 10 years ago, if I went into a certain type of restaurant, I'd pay similar prices no matter where I went and would probably have a perfectly decent meal. But now, the pricing AND the quality is just so incredibly variable that it makes me a bit suspicious.