OK, since you asked, I'll show off my stuff
These were all made as costumes and props for fan films that I have done for YouTube.
My lightsaber collection. All were made from plumbing parts and various scrounged pieces of stuff lying around. None cost more than $15.
My Predator spear, made from two toy "laser swords" and a length of PVC pipe. Total cost around twelve bucks.
The Predator head on the left was made from a modified Rubies Deluxe mask. I added teeth, dreads, and bristles. The bio masks were both made from posterboard coated with fiberglass resin. They cost about five bucks each.
My Scout Trooper. The helmet is a Rubies (I made this costume before I ever heard of pepakura). The rest is scrounged from a sheet of vinyl, some plastic two-liter soda bottles, some soccer shin guards, a black jumpsuit, and some motorcycle gloves. Aside from the helmet, the cost was about $45.
My X-Wing Pilot. The helmet is a Rubies; with an orange jumpsuit and black boots. The vest is a tank-top t-shirt with strips of aquarium tubing attached using white medical tape; the chest box is a carboard box with greeblies (the round silver thing is a lawn sprinkler head) and sump-pump tube. Aside from the helmet, the cost was around $50.
My Imperial Gunner helmet. Made from a toy Army helmet; the shrouds at front and back were made from craft foam. Total cost about $15.
My Alien Xenomorph. The head is made from taped-together posterboard covered with fiberglass resin and tubes; the teeth are press-on fake fingernails; the body is a black morphsuit with pieces of foamie and tubes glued to the limbs; the chest/back is a vest made from craft foam, with tubes and more foamie at the front, and four pieces of pool noodle at the back; the tail is a length of sump-pump tube with a wire running through it, with pieces of foamie glued to the outside. Total cost came to around $75.
My Klingon. The latex headpiece that I made unfortunately got a big tear in it from an accident; it's replaced here with a trimmed-off Word mask. The armor is made from strips of vinyl attached to a long-sleeve shirt; the sash is a piece of textured vinyl; the disruptor is a water pistol with the front cut off and replaced by wooden dowels and pieces of foamie. Cost was around $50.
My facehugger. The body is made from two layers of craft foam with a wire frame in between, and two balloons; the legs and tail are foam backer rod coated in latex. Cost around ten bucks.
My Alien Xeno egg. Made from craft foam and filled with sprayable insulation foam. It has fishing line running through aquarium tubing so I can open it off-camera. Cost around $20, and most of that was for the Great Stuff sprayable foam.
Three complete Predators. The bodies were done from a Rambo fake-muscle chest and a pair of leotards. The bio masks are posterboard/fiberglass resin; the armor is rubber car floor mat; the gauntlets are shin guards with foamie greeblies. Total cost was less than $200 each.
A budget build in the works: this will be a set of Roman lorica segmentata armor. It's being made from sheet metal, some brass cabinet hinges, and some scrap pieces of leather. Total cost will be around $50.
To see my fan films, go to YouTube and look for Lflank's channel. There are also build films for most of these.