I bought a 8×16 floating dock for $100 delivered. The main reason it was so cheap was that they had originally used Melamine covered particle board for the decking, with predictable results.

But the pressure treated 2×6’s and foam floats were in relatively good shape, so I bought 4 brand new 2×6’s to have nice new lumber on the outside, and built my own 8×8 floating dock.

I used 7 2×6’s total (4 new ones and the 3 interior ones salvaged from the original dock) to build the frame around the foam floats, wheeled it down to the lake, and then screwed in 19 composite deck boards.

And here is the finished product (before adding hardware to fix it in place with pipe floats, bumpers, solar lights, etc…)

The total cost was about a dollar per pound of dock. The composite deck boards were the heaviest and most expensive single item, although the hardware to hold the dock on pipes and attach it to other dock sections will also add significantly to the cost.