No single file of source code should ever be even close to 200MB, and no data file (CSV, XML, etc) of that size should be manually edited in a text editor.
Vim and Emacs are quite well-suited for textual manipulation of very large data files. Use of a macro is a very pleasant alternative to piping the file through sed/awk/etc. for a once-off transform.
This sed substitution thing seems to be a cute trend to express "fixed that for you". It goes nicely with programmer's propensity to express themselves in needlessly arcane ways.
Wrong tool for the wrong job.