Hmm - we recently did a 4 course meal for 40. I think you're right about the cutlery etc, because that was where we fell down - we had enough for 40 at once, but not enough for 4 x 40, and so we kept frantically going round grabbing plates and washing them up. However, it does make it easy to feed poeple cheaply, because you can do things like gazpacho or onion soup, which look posh on little money and can be prepared well in advance.
Could you do a few big tortillas (maybe with different additions, like chorizo or asparagus etc), and cut it up into canape sized pieces?
Chorizo bits on cocktail sticks?
Cheese and bread went down very well at our do, and is good value.
Little cherry tomatoes with a basil leaf on them?
Smoked mackerel pate? cheap to make in the UK at least.
Ah - I know! Empanadas! Cheap as chips, finger food, and everyone likes them. Do a big dish of tuna empanada, a big dish of meat empanada, and then a veggie one.
Could you ask a relative to bring over a Scottish smoked salmon? It's the kind of thing they like to bring, don't you think?
And could someone bring some mini oatcakes, to serve with smoked mackerel pate on ?