Originally Posted by Retro Grouch
What if the bike shop guy had just said to you up front:
"I really don't want to get involved in trying to upgrade an old French bicycle. It can involve lots of time chasing down hard to find parts that still might not work. The parts are almost sure to cost much more than the bike's worth. In the end the bike shop is unlikely to get paid for all of the time involved and the customer is unhappy with the result. It's almost sure to be a lose-lose proposition."
The mechanic should have been to the point, as in "I know you would like to upgrade your bike but it is likely to cost you more than you realize, probably at least $
n and maybe a lot more. And since it is an older bike, sourcing the parts needed to fit it the way you want will take longer and cost you more in labor than doing the same thing for a newer bike. Since this is a sentimental project, and the bike's value will still be less than the cost of the work, you will need to pay up front. Don't take it personally, but that is just how I have to do business of this sort."
Then you could have decided whether you wanted to do this with him or not. Blowing you off wasn't right, but maybe he has been burned before on drop-off work no one came to collect. At the same time, you should be prepared to pay in advance most of the estimate. That is only fair, too.