Depends on which bike.
Runs the range from the Specialized Stumpjumper that I then laced up some 700c rims to XT hubs for a disc "hybrid" back before there was such a thing and that cost around $2400 in total. By far the most money I've every spent on any bike by at least $800. But it's got an XTR rear derr so I guess it's not a bad deal.......
At the other end of the spectrum are a couple of old Norco bikes. One an early road bike set up as a single speed. Total investment around $150 if you don't count the Brooks saddle on it at the moment. THe other a Norco Rampage MTB in Tange Ultimate tubing that I have around $250 invested. The other couple that see commuting duty are in the middle.
Oops, almost forget the new addtion. $650 for a Redline 925 single speed. It was supposed to replace the aging and starting to rust Norco SS. But the Norco just feels SOOOOO nice and it has that way of looking at me so I can't part with it.