Sorry, just finished Sunday lunch!
A rudimentary way to work out the cost of a menu item is to calculate how much all the components of the dish cost and then multiply that by 4, which should give you a gross profit of around 65/70% (industry standard) - out of that g.p. comes VAT, wages...
It depends on what ingredients are going into the dish (truffles are expensive, for example) , but I would broadly agree that veggies and vegans get an unfair deal.
One consolation is that there is a lot more options than there ever used to be, and even the smaller places will have a couple of...