I have bought dozens of barrels over the years. Most were at gun shows for 100-200. I also have fit maybe 15-20 to my own guns. The amount of work involved varies from a hour of tedious minor fitting to you just can't get there from here. Most times even very close serial numbered guns are not likely to be close in fitting. Fitting barrels cost what they do because it's worth it just like a good divorce.
I found that just by taking multiple measurements I could weed out the worst barrels from the start. Doll head extensions are a pain in the zss to fit and make a nice looking job. Then you get into early or late barrel versions. Just because they were made by the same maker does not mean they are really the same barrels. I love Lefevers but they seem to have 79 different barrel combinations. I guess each barrel was struck to the action so no two are alike.
Anytime you hear a seller tell you fitting barrels is a half hour job ask to see what his half hour job looks like. I saw one that they had filled the gaps with JBWeld. That was a nasty looking half hour job. So if you want an extra set of barrels fit to your gun send both to a decent gunsmith and let him evaluate them. After all he's the one going to be trying to make that square peg fit into that round hole.
