1. Cosplayers have to make every piece of their costume.Although many who cosplay are focused on crafting their entire costume, it is definitely not a requirement! Even the best cosplayers will order or commission pieces that are outside their skill level. Someone may be excellent at sewing, for example, but rubbish at prop making, and choose to purchase from an experienced prop expert.
Moreover, it's not a bad thing to purchase items for your costume! My personal rule is if it's cheaper AND easier to buy (or modify) a piece, and it's still accurate, I'll buy it instead of making it from scratch. Some costumes lend themselves to purchasing rather than making, anyway.