I spent much of yesterday helping customers that had existing performance bike achieve a more upright position, and lower gearing. This involved changing out the drop bars for flat bars, adding short riser stems and replacing the brifters with flat-bar shifters. Some derailleurs had to be changed because of shifter/derailleur incompatibilities. Cassettes were replaced with pie-plates, which involved changing out the derailleurs and the chain.
So a minimum of a few hundred dollars of parts per bike, and up to several hours of shop time.
I figure the racey-type bikes we worked on cost on average $1,500 when new, and then we added roughly $500 of parts and labor. The owners of these bikes could have had a more appropriate bike and better overall ride experience if they had originally bought a $1,000 hybrid, which they've now almost ended up with.
This doesn't factor their inability to use better brakes (such as V-brakes), and fatter more comfortable, flat resistant tires.