Boat lift help!!

Hey guys,
I'm considering investing (err throwing money away) on a lift for the xstar. I know there are tons of threads out there on lifts but my situation is very unique.

I'm a member at a boat club on a river that has floating docks with lots of depth (10') and a muddy bottom. Water level definitely varies about 4' throughout the year. The docks are old as sin, and couldn't support any sort of lift attached to them (like a hydrohoist setup). I don't believe the club would allow me to put a lift that sits on the bottom as we take the docks in and out every year.

So... what I'm left with (I think) is a self-floating lift. I have a buddy at the club who has a sunstream floatlift and the thing is awesome. They sell new for like 14k and I don't want to dish that out on a lift. Any other options out there?

I have another friend who has a sunstream V-lift (air displacement but still floats on its own) slightly used I could buy for 6k (overpriced?) that's in town. Lots of money but do I really have any other options?