Practical effects are expensive for starters, before you explore costumes, sets, props, lights, camera equipment, makeup, feeding your cast and crew, etc. etc.
I know this is a rather ridiculous thing to ask but I'll continue. Basically I have this idea about making a full feature length Alien fan film. Not 8 or 11 minutes long but 2 and a half hours.With the same kind of practical sfx you would see in the early 80's i.e. Lots of well filmed miniatures and animatroncs (V little CGI) I'm working on the script and I'm putting together some kind of business plan to make it viable to investors without annoying Fox (in theory). The story is a revision on Weyland Yutani, the Alien and the heroine will be quite familiar to you all already but at the same time it's a complete revision of her character (well.. mostly) All suggestions welcome.