I'd bet it's the same job more often than not. For example, when I go to a restaurant serving steaks, the job isn't significantly different from one steak to a

I'd bet it's the same job more often than not. For example, when I go to a restaurant serving steaks, the job isn't significantly different from one steak to another, but the cost can be significantly different. Preparing a ribeye vs. a t-bone vs. a sirloin isn't all that different, but you can expect the prices on each to vary wildly, mostly due to the cost of materials. Rationally, neither the wait staff nor the chef really deserve more of a tip for one vs. the other, but the convention demands it.