That is a hell of an awkward situation.
The first question is, do you enjoy going? If you don’t, just bow out if you can.
The second question is, do you need to go for business reasons? In some offices, staying behind when everyone went ot a good-bye lunch would be like spitting in the face of a threee year old nad running off with thier candy. In others, it would be no big deal.
Third, how often does this happen? If it happens once a year, I’d say suck it up, it’s inconsiderate, but there you go. On the other hand, if every office occasion is answered this way and it is happening monthly or more often, then you have to change it.
If you have decided you either want to or need to go, and it happens offten enough that it is an issue, then what you need are allies. You probably weren’t the only one who was trying to be economical, only to discover that you economy resulted in subsidizing other’s indulgence. Find these people, and mention in passing that it really sucks when that happens, you’re uncomfortable, yaddie-yaddie-ya. It helps if some of the people there who ordered the appitizers, drank $5 beers, etc, make alot more money than you. People are usually happy to bitch about the inconsiderate nature of managers. What you want to do here is foster a groundswell of opinion that seperate checks are the fair way to go. You don’t want this groundswell to be focused on yu, so you start by bringing it up casually to a couple people you know will agree with you, bring it to the forefront of thier mind, and let it grow. Once the idea comes back to you, you can agree with it, point out good reasons for it.
When you bring this up you want ot appear torn not greedy or whiney. Be like “You know, I have so much fun when we go out to eat, and it’s such a great break from the day, but the other day I had a $25 chicken sandwitch, and twenty five bucks is alot of money in my house these days.” If you play your cards right, you should only have to say it once, to the right person, then feed hte flames a bit when it comes back to you. Like I said, oyu are almost certainly not the only person who is unhappy with this.
Another technique is to go, but don’t eat. Say that your on a crazy diet, or that you had a huge breakfast, or that you’re having a huge dinner, or that your stomach is acting up (that won’t work weekly) and just sip an iced tea. No one will expect you to put in if you’ve only ordered one soft drink. To carry this off you have to make it clear that you really are happy to be there, jsut there for the company, enjoying yourself. Put a couple bucks into the tip pile, and grab some chips on the way back to the office.