New, I think that Quaife's and Kaaz's are around a $1000. Spoon, ATS and Cusco are some other brands. Don't forget the option of a JDM OEM LSD from a CTR or ITR for around $385 used. Then you have to factor in the cost of installation of it.

Some like Quaife because of their lifetime warranty. My boyfriend had a Kaaz LSD in his GS-R, then switched over to a Quaife. He liked the Kaaz better and will be selling his Quaife at some point. I have an OEM ITR LSD installed in my GS-R sedan and like it just fine.