For a 3-night retreat, we were aiming to cost no more than $300/person (including food and lodging for all 3 nights), and we hit that number right on the nose.
We started out by taking $150 deposits with PayItSquare, which is a cute little thing that hooks a signup sheet to your PayPal account. It makes it easy to send out a single link and let attendees see who has signed up already.
We tracked our costs (mostly food, plus a few other supplies) in a google spreadsheet during the rest of the planning, and people paid their balance after camp was through.
The breakdown of funds went like so:
| Barn for 3 nights | $1801 |
| Pens & Notebooks | $60 |
| Wall post-its & markers | $34 |
| Admission fee to the bird sanctuary | $100 |
| Fancy sodas | $39 |
| Alcohol | $165 |
| Lunch (restaurant) | $268 |
| Groceries (organic, local, etc) | $813 |
| Total | $3280(AKA $298/person) |