Here's my lobster costume for Halloween ... for under $25!
Step 1: Supplies
1) Approx. 30 large red plastic plates... < $5
2) Approx. 40 9oz red plastic cups... < $5
3) Red hat (fleece)... ~ $6
4) Red duct tape & clear packing tape ~ $4
5) Red string ~ $2
6) 4 small squares of red felt... ~ $1
7) 2 Styrofoam balls and googly eyeballs... ~ $2
TOTAL COST: < $25 !
I can't even begin to describe the 8 hours that went into making this costume... but you get the general idea. Probably more tedious than difficult. The packing tape adheres quite well to the plastic, so you can get pretty creative with the layout and appendages. Just make sure to leave some room for flexing so your tail doesn't crack!
...and if all else fails, you can just volunteer to bring the cups and plates to the party!