The subject of kaffir limes leaves has come up before. Central Market sometimes has them for $80/lb. 6 leaves would have cost me $2.60-something. I put them back.
I have since gone down to "It's About Thyme" nursery in Manchaca and bought two trees. They have small trees starting at $7. For $12 you can get one with about 50-60 leaves on it. So I got two trees. One to grow, and another I ravaged for immediate use. They cost far less than what you'd pay at CM. Plus you can GROW them (preferably in a pot that you can take indoors during freezes). They have a couple hundred of them in in $7 and $12 sizes.
They also have 4 or 5 very impressive full grown trees. I think they're too big to get out of the greenhouses in which they grow! They are big, beautiful trees busting out of their small pots with leaves up to 8" long.
They also have lemongrass, galangal, ginger, bhut jolikia, Thai eggplant, and a bunch of other peppers just starting. If you're into Thai cooking and want to grow you own, this is the place to go.
I have no affiliation, etc, etc, etc...