I like the T-Shirt-idea of @gina: Have several "generations" or shirts, different colors, different designs - but no event names or years printed on it. So we can sell shirts as long as stock will last - and have different kind of shirts available.
Taking the idea of @fheinze a step further:
For "expensive" swag (e.g. mug) we could put a box there for donations and then maybe give the money to charity.
Why not have a swag-booth with different things and a "proposed price"-tag next to each article. This tag could show two prices:
- the minimum price that would cover just the production cost
- the recommended price
Everyone could then choose how much he/she will spend on an article. This will basically open a certain risk of having less money in the box then needed in the end - but on the other hand I see a way bigger chance that the event attendees will take 2-3 items, sum the recommended price and round up to the next bill (banknote) and in the end there will be more money in the box than actually spent for producing the items.
In this regard, I'm not against investing part of the win into charity - but I think it's probably more complicated than just saying "the win of these merchandise sales goes towards the Neos project" (e.g. for paying code-sprint food+beverage or similar). I think giving money to some charity is well worth it - but will lead to a discussion as each and everyone of us probably has different preferences.
So this will just "cost" money temporarily for pre-financing the pre-event production of stuff - then money comes back after each event. Thus the budget is more of a buffer (and risk) position than a fixed investment.