[nine_k]

Machine code duplication is spending a few extra megabytes on perfectly valid, if duplicate, machine code.

Source code duplication is a risk of spending an hour, or maybe a day, of developer's time to detect the duplication, change it in concert in several places, with an occasional need of detecting and fixing a subtle discrepancy between the copies.

RAM is $0.015 per megabyte. Developer time is $50 per hour.

[jesstaa]

You could also spend that developer time trying to untangle code reuse between various components, or the more subtle breakages caused by changes that don't account for the expectations of all callers. Code reuse is still a tradeoff.

[the_af]

It should be noted that generic code is harder to break. It is, by definition, less entangled with its callers. There are also fewer operations you can do with generic parameters, so there are fewer ways to screw up.