Not sure which lake you are on but you most of the LOTO crowd uses dockrealty.com when dock shopping. That only works if you aren't looking new. You can get some decent deals on here from people upgrading to larger docks for new boats. Especially right now with the market being slow. Slip width, decking materials (contrete vs decking vs marin plywood etc.) and foam type make a huge difference as well.
But to answer your question I would expect to start at $8-10K for a solid dock with encapsulated foam. You could easily go $30+ if you went new with concrete, storage and some other add-ons.
Just like he said ,,from looking around on Lake Travis I saw some nice deals by shopping used from people looking to upgrade. go on craigslist for your area and search for "dock" and youll be suprised how many you find especially on Texoma.
My brother-in-law had a dock custom built last year. His is for single, 25' boat and has walk-around and upper deck. It is steel frame and the deck is that stuff that never rots (?). I believe he paid $25K