Athame's don't have to be made of metal, they can be made of wood, bone or even antler.
Here's a pretty cheap and effective way to make your own athame.
Find a suitable knife. You can purchase a knife at any store, find and carve a piece of wood or use a knife you already have. Make sure the knife fits comfortably in your hand and has a pleasing shape.
Set out all of your materials in a quiet space where you will be undisturbed. Set most of your candles in a rough circle around the room. Make sure none of them are in danger of catching anything on fire. Retain one candle for the center of the circle.
Set out two bowls, your extra candle and your incense in the center of the circle. Pour water into one bowl and salt in the other. These represent the elements with which to consecrate your athame.
Spread your knife and craft supplies out in front of the elemental offerings. Light your circle of candles, then turn out the lights.
Sit in front of your supplies and close your eyes, breathing deeply. Take the knife in your hands and visualize how you intend to use it. Imagine your intent moving from your palms into the knife. Light the candle and incense.
Put a drop of glue on the handle near the top and press the end of the ribbon into it. Wrap the ribbon down the handle, overlapping layers to cover the handle completely. At the bottom of the handle, snip the ribbon free of its spool and glue down the end.
Wrap the handle in more ribbon, if desired. Use narrower ribbon or another color to crisscross over the first layer. Focus on your intent while you wrap, imagining the knife's purpose being bound up with the ribbon.
Pass the knife over the candle flame and through the incense smoke. Sprinkle some water and salt over the blade, envisioning the knife taking on qualities of each element. Hold your new athame in the air over your head and feel the power radiate from your hand into the blade.