I bought a new outer cv joint for my A4 wagon off ebay for $50 delivered from Sydney, including the boot, grease and a new bolt. If you just need one joint I don't see the need to blow money on a full axles. I am assuming you don't mind getting dirty.
I don't know if this next observation has any value but before coming to Australia in 14 years of running VAG vehicles, I don't recall replacing any CV joints at all. The odd boot or 2 but no CVs. Since 2006 though, I must have done half a dozen, that's just on personal vehicles no one elses. That includes 2 inner CVs which I never came across back in the UK.
I'd love to know why????
Gavin