Even for frames that have never been in a front end collision, this is an extremely common failure point, because of the high stresses involved. Another is the seat-tube-to-BB-shell juncture (been there ... done that with a 1971 Nishiki Competition, after 20 years and about 40K miles). You are correct in your economic analysis, which is why I scrapped the Nishiki (and the Peugeot UO-8 that broke at the chainstay, between the tire and chainring clearance dimples).