YOU....since you brought it up.  

Sorry, that was just too easy.   Hope someone posts a legitimate response to your inquirey.

When I was in HS (a bizzillion years ago) - the cast party was usually hosted by those who fit one or more of the following;

1. Big house with a pool
2. House was close to the school
3. The parents wanted to host a party.

Basically whoever volunteered first - no matter if it was the person playing the lead, chorus member or techie.

In my experience with HS productions, the cast parties are hosted by:

1.  the director

2.  one of the other teachers involved in the production

3.  the presenting class, usually in the school cafeteria or gym, using class funds

4.  at a local restaurant, with reservations made in advance, parents present, and each student paying his/her own way

5.  but usually by parents of one of the students, not necessarily the lead.

I always pray for a parent to volunteer (they usually do, thank God!) so that choice #1 doesn't come into play! 

During the warm months, any home with a yard and pool is a big hit. We did Grease in May, and I still am finding shirts, towels, shoes, you name it. During the colder months you need someone with a big house. Anyone in the cast, or crew, that is willing (and has permission) can host it. Once I have a volunteer, I doubt check with their parents to make sure they are on the same page, and if they are going to supply the snacks, food and pop, or order pizza or subs, etc. Determine whether the kids need to pay to eat, how much $, how long can they stay, etc. I need to hear back from the parent  before it is announced!  Then I post a sign up sheet with all the info, so they will know how many to expect. It is a huge undertaking!

I'm usually too overwhelmed to care much about the cast party at the end of the run.  I usually list on the rehearsal/performance schedule.  We talk about it as we close in on tech week.  Either a parent volunteers the house/whole party, we have it in the rehearsal hall, or we go to Denny's at the conclusion of the performance.

Pay - drama's budget is always in an iron lung, so if the kids want a party, they gotta pay.  We usually do something cheap like pizza and have the kids pot-luck the plates, cups, soda, starters/chips, and dessert.  We generally charge $5 to cover pizza.

If we go to Denny's, I get a menu ahead of time and tell them to bring enough money to cover what they want to eat + 30% for tax and tip.  I also bring a lot of ones for giving out change (we have them do 1 ticket for every 4 people--a little easier than 1 ticket for 30).

The kids I'm working with now have never memorized a line in their lives, let alone even heard of a cast party, so I'm not mentioning it.

However, when I was in HS doing theatre I would always plan a trip to the local Pizza Hut (speaking with management in advance).  It was "buy your own", but we always sang for our drinks ... soda is cheap.

In college, it was usually whoever had a big house out in the country and wanted to have the party .... oh, that would have been me, too! 

Nanette - you may be missing out on a wonderful opportunity here.  The last time I did BCPE - I called the local movie theatre and got a PRIVATE morning showing of whatever kid's Christmas show is there. This year you have "The Escape Clause". The theatre gave us a break on the price, which included popcorn and a small pop, the kids were encouraged to bring a friend, parents and siblings.  Everyone LOVED it, several years later they still bring it up.  WIN-WIN - not much work for you and it leaves a lasting final FUN memory of their time together.  It makes them want to come back and do more that is if you want them back  LOL