990S Rear Shock Service Cost

Hi,

My rear shock has sprung a very small leak, so I figured now would be as good a time as any to get it serviced.  What sort of costs am I looking at?

I got quoted what seems an batshit crazy amount (R23K - I have requested clarity on that).  For what it's worth this is what the quote includes, and this is with me removing the shock from the bike:
- Shaft seal,
- Bush,
- O-rings,
- Nitrogen,
- Oil
- Labour

Thanks.