It's not been mentioned yet, but the cost of the re-plating itself is certainly a factor. If the cost of the brassed razor was $10, and the re-plate job is $20-$30, then you have $40 invested in the razor. $40 will buy a very nice condition Old/New, and you could thus avoid the re-plating all together.
If the razor has some sort of sentimental value to you (such as being your first DE razor, or a family heirloom) then perhaps the re-plating is worth it.
My first DE razor was a well worn Ball End Tech that was PIFed to me by a kind gentleman on this forum. It has since been re-plated, as it had value to me as my first DE razor.
If you've got a common razor and it's in poor shape, then replating can only increase it's value, especially to you! I see nothing wrong with replating a razor when there are so many totally brassed and green News and Old Types, etc. We all want to own and shave with nice and shiny vintage razors and there are only so many of those to go round.
If you actually have some rare vintage razor then I'd weigh the pros and cons. But if it's common and you intend to keep it, then it's really your prerogative.