The best way to ask guests to pay for their own meal at a restaurant is to make it clear that the people inviting them are acting as coordinators and not hosts, according to Emily Post. If people invite guests and say that they are hosting the dinner, then guests will expect that they do not have to pay for their own meal.
How the invitation is worded is important when inviting others to dinner and phrases such as "let's split the tab" can make things clear. Some people may want to host the dinner at a restaurant, but cannot afford to cover everyone's meals.
There are ways to make the dinner less expensive. For example, hosts can invite less people or have a appetizers-only menu at the restaurant. Another option is to host a potluck dinner at home.