You can low cost by going with a refurbished combined, but it's still going to cost $35 to $90 and may not hold up as well as a company new combined longevity will vary with regards to the fixing process used some joints and lower back are removed using large elements to cover for wear while others are re machined to recover like-new building up a tolerance. for other info about CV joint replacement you can contact you auto repair man for it or have a service manual for easy replacement.

I've never done it myself but if you're mechanically inclined and have proper instructions give it a go.  Do your homework, here's a few articles that might help give you a better idea if you can pull of the CV Joint Replacement