It's often not the same job behind the scenes. Your more expensive meal typically requires more effort to prepare. The other function of cost is drinks and if you order more drinks then you require more service.
If you've not seen how the back of house functions you may have some misconceptions about the sources of labor involved in your meal.
This is a generalization that isn’t universally true. I’ve known so many restaurants where the servers keep their tips. The whole point of this thread was that the means of application are inconsistent and arbitrary.
Least expensive item is a salad at $7. $0.70 tip. Most expensive is $22. $2.20 tip. This is a baffling thing to care about.
I want to know how it works! You’ve told me I’m ignorant and that’s fine, I’m too invested in my current career to get a job in a kitchen right now, and you seem to know, so go ahead and educate.
Who gets my tip and how is it divided? I’ve always assumed it goes entirely to the waitstaff (pooled or not). It seems like maybe it should be distributed to other people who make the service happen. Does the dishwasher get a cut? What about the line cooks?
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.