tarwheel 

I'm buying an older steel lugged frame that doesn't have water-bottle mounts on the seat tube, although it has them on the downtube. I know that I can buy clamp-on bottle mounts, but just curious as to what it would cost to have them added by a framebuilder. If I did that, I would probably have a pump peg added to the head tube and perhaps an extra set of fender eyelets for the rear dropouts. (It has one set but might want two so I can add a rack as well as fenders.)

Any estimates on what it might cost for these braze-ons? I assume that adding the drop-outs would probably require me to have the frame repainted as well, but just wondering what the braze-ons would cost by themselves. I probably wouldn't have the braze-ons added unless I decide to get the frame repainted.

JohnDThompson 

The easiest way would be to use RivNuts instead of a braze-on. The heat from brazing bosses into the tube would damage the paint around the bosses, while with RivNuts all you need do is drill a hole and install the RivNut. They're plenty strong for this application, and are commonly used on aluminum frames right from the factory. Many bike shops have the tools to do this, so check around.

unterhausen

some people will try to repair paint for braze on modifications. Depends on how much of perfectionist you are. I am thinking the cheapest you can get water bottle mounts brazed on is around $25. Pump peg about $10. That's for people that don't value their time and have no imagination for what they could be brazing if it weren't for helping people that want a second water bottle.