Gold plating thickness?


I am a jewelry designer from the NY area who is starting a line in
brass which will be gold plated. I have no experience in costume
jewelry, until now I have only worked in gold and silver… I was
wondering if anyone knew what type of plating is generally used by
custom jewelry designers (such as Kara Ross, Kenneth Jay Lane)?

One plater told me he charges $40 to plate a ring with 5 microns,
but that price is would make the final jewelry too expensive…
another one quoted $5 but said the type of plating is different and
is less than 1 microns… Of course I don’t want the plating to wear
down so fast… Is there a “standard” for this? Wondering if someone
knows and could help.

Thanks in advance, much appreciated