That would only be true if both the old and new bikes are extremely cheap $150 department store bikes. His bike has brifters. Even assuming lowest end components, we are still looking at a $600-700 bike. There is no reason why he should have to buy a new bike for just a handful of parts.
Given the OP hasn't given any bike specs, say 10 speed flat bar shifter, R770 or even R440 aren't cheap, and SRAM's version is even more, neither are the rest of the parts needed, I did say do the math, as in work out what is the most cost effective option, factor in the condition, as mentioned, then work out what is cost effective, maybe work out if it is cost effective, not sure if I said that a few times in my original post, do the math....