I just upgraded my water system from the standard foot valve in the lake and Jet Pump to a Submersible Pump and Filter system.
I contacted Gilford Well and got a price from them, my jaw dropped to the ground after I received their quote $4900, their material prices were inflated 2-3 times the costs I found.
I went on-line and using their itemized material list bought everything I needed for $1700. My system consist of a 1/2 hp submersible pump by Gould’s inserted into a PVC pump screen by Lakos, I built a pump stand using 1/2 PVC and filled each section with sand to help weigh it down. The pump sits in 8-9 feet of water and is about 140 from shore, deep enough so the ice won't bother it. I purchased 300' of 1" poly pipe (160 psi) from Heath's hardware which runs from the pump to the back of our camp where we have an enclosed and insulated pump house. In the pump house is the pressure tank, a sediment filter, a carbon filter and UV filter. Of course there were miscellaneous pipe fittings and electrical components to make it all work.
We are not drinking the water yet but that is our plan once the water has been tested.
Bottom line is how sophisticated you want your system to be will dictate the price.
I purchased most of the bigger items from this company
http://www.aquascience.net/
This is the basic diagram I followed (minus the well casing):
http://www.aquascience.net/submersib...?well_system=1
Good Luck