Around $23.00. That's what a simple wrist corsage with two roses, some greenery, and a bow goes for at a local florist. Save yourself some money and make it yourself. A bunch of roses and baby's breath should cost around $10.
Besides that, you'll need: A bow (another tutorial for another day), scissors, needlenose pliers, wire cutters, chenille stems or floral wire, florist tape, silk leaves, corsage pins, and a wristlet (if desired - and all the high school girls desire them. No one wants to pin one to their dress anymore.) Almost all of the stuff is available at Walmart - although I have to buy the wristlet's at a local ribbon outlet.
Begin by cutting your flower with about a 1 inch stem. Remove any ugly outer petals and sepals if you wish.
Poke a three inch long wire or chenille stem up into the hypanthiam (base of the flower) - you can just poke it in, or thread it through, it will depend on your wire and your flower.
Then begin to wrap a piece (about 10 inches long) of floral tape around the base of the flower, as close to the petals as possible, completely covering the wire.
When you have the top covered, then attach a silk leaf with the tape, and add some greenery before taping down the entire stem.
When you get to the end of the wire, tape back up the stem for a half inch or an inch then pull the tape to break it off and press down the end.
To finish a Boutonniere, take the end of the wire in your pliers and curl it up.
Add a pin and your boutonneire is finished.