They're available in carbon, or stainless.moras are nice, but remember, they have the "ability" to rust
$10 gets you either a molded plastic handle or a red dyed handle, both with plastic sheathes. $28 buys a 'deluxe' model with a raw wood handle and leather sheath.
Opinels are wonderful cutters, my favorite knife. But to stay under $10 at most dealers, you're going to be limited to the smaller models or paring knives. If you can spare $3 extra, the Mora Garden Knife is an incredible bargain.