I dunno, maybe where I live groceries are really cheap but $30/person is way over the top. I just bought a 15lb turkey for under $5. No one says you have to make 20 different sides but honestly, I think I could easily bring in a TG meal at around $5/person. And that would also include having leftovers.
I don't do TG, my sister does, but I buy a turkey anyway because they are so cheap and cook it later. I do host Passover though, and spend much more than $5 on a brisket, and counting that + sides, I probably come in at somewhere around $10 per person, again, with plenty of leftovers. And trust me, no one goes away hungry.
In any case, the only way I could see charging is in the example upthread where the host is going to have it catered because no one wants to cook and everyone agrees in advance to split the cost of the catered meal. Otherwise, you either make do with what you can afford or do a pot luck or let someone else host or all go out for the meal.
So put me in the "incredibly rude" camp.