The author explicitly states that he used to order on the lower end of the scale but, being unable to change the attitude of the group -- the majority of which were ordering on the high end -- he decided to stop subsidizing their meals while he goes without on his own.
"I developed this system after too many birthday dinners where I went home poor and hungry. This way, at least, you get the food you want."
Honestly, I can't blame him. Would you want to order $30 worth of food only to be expected to contribute $170 to the meal? That's nearly SIX times the amount you ordered. Meanwhile, you get only a small dish or maybe just an appetizer and drink water, so you're not completely full (unless you're a very small eater to begin with), don't get the drink you wanted, and have to eat Ramen for a *week* at the end of the month because the extra $140 has to come from somewhere in you're budget and if you're on a tight one (as many grad students are -- I seriously don't know a single one, who doesn't have a trust fund or very generous parents, who hasn't overdrawn on their bank account at least once to cover basic necessities) it probably means skipping on a bill or skimping on groceries.
Can you decline the invite? Yes, to the risk of you're friend feeling very hurt and like you're not as close as s/he thought you were.
Can you insist on only paying your portion? Yes, but you come across as a cheapskate and jerk because you're begrudging others. This can also impact your rel@tionship with your birthday having friend. (And, honestly, I don't think anyone can argue that people aren't looked down upon if everyone else agrees to split the check evenly and they insist on splitting their portion only. People who go against the grain with money in such a way they're trying to pay less aren't looked upon fondly. It's more "I'm splitting the check evenly and I only ordered $150 dollars worth of food, so what's wrong with you that you won't suck it up for the group?")
At which point the only halfway reasonable option is to order food enough that you'll not be paying six times your own bill.
Again, I guess one of the issues I have with this is that if everyone acts like the author, the only winner is the restaurant - because everyone will just order more and more. It's like avoiding the issue instead of dealing with it. I think that there are ways to pay for only your portion without sending the message of begrudging others - because in fact you are indulging their desire to want to order lots of expensive things. But most people would understand this.
One tactic is to be pre-emptive, and actually excuse yourself before the check comes. If you know what you've ordered, do a little math for the tax and auto-grat, and pull out what you know you owe while headed to the restroom and say "Excuse me, I need to use the restroom, this should cover my meal and drinks" Be explicit - there is a really good chance others will follow suit. In large group situations people aren't always aware that one person has significantly under (or over) ordered - and because people are lazy they opt for the split X number of ways. If you wait to say, "I'm only paying $Y" until after someone has announced how much everyone owes - people will be annoyed because they've already figured it out and now they have to do more math. If you address the issue head on, it's less likely to be an issue. As I said up-thread, I've never been in a situation where the check was just split evenly if people hadn't all ordered the same thing. That's not just luck, its also being upfront about expectations.
In terms of declining an invite, if someone doesn't learn to politely decline invites, they are going to be in a world of hurt later in life.
Re: bolded As a grad student, I know many grad students who have never overdrawn their bank account (necessities or not) without the help of mom, dad or a trust fund - myself included. It's not necessarily an easy thing to do, but plenty of grad students do it. Perhaps not the ones that haven't learned to say no to $140 dinners though... Honestly though, I understand that money can be tight. Which is why the writer's approach is so awful to me - it's not addressing the issue. He's still blowing his budget on one meal out. But then (unlike the rich lawyers he complains about), he has the nerve to gripe about how much it sucks that people order expensively - when he is doing the same thing. Except without the plausible deniability that he was just ordering what he wanted to eat that the rich lawyer has.
And I'd like to reiterate that for me it's about the attitude that he has in his article and his rationale. If he went out and ordered with reckless abandon because it was going to be his one night out that month and he was going to have a good time, well then darn it, I'm with him 100%! Just like I'm with the grad student that eats ramen for 11 months straight and doesn't turn the lights on so they can afford afford a fun vacation that year. It's the "offensive ordering", while complaining about the whole practice and having to pay a large amount of money because he's basically forced to order the expensive thing because he's too immature to deal with the issue head on that bothers me. And I'd also be bothered by the grad student who complained about the fact that they ate ramen for 11 months in the dark to afford to go on the cruise with a bunch of their lawyer friends who had more money.