At one time gold nibs were important because inks corroded steel nibs. Now with the advent of stainless steels and other metals this is not an issue. But gold nibs are often a sign of a high quality pen and are likely to have more careful quality control. Steel nibs are likely to be made by the tens of thousands and dumped into big bins. It doesn't have to be so, but often is. However, if I company decides to use steel and to make the best nibs they can make (as Sailor is currently claiming to do), they can be as good or better than gold nibs.
The cost of the gold in a 14K or 21K gold nib is around $40.The bottom line from Doodlebud's video is, "it depends" and there are lots of other factors involved.
Some of the best pens have gold nibs with some kind of platinum group metal alloy plated onto it to give a "bicolor" effect. That is not what we are talking about here. Apparently Rhodium is often used. It does seem a pity to hide that gold though, but some nice pens have bicolor nibs because it looks cool.
The "iridium" nib label is by and large a marketing lie. There, I said it.
I once read an article by some fellows who worked at an aerospace lab
and were able to take their pen in and put
the nib on some instrument (probably a mass spectrometer) and found that there was
no iridium whatsoever in the so called iridium nib.
The so called iridium is most likely a stainless steel alloy.
Gold, even 14K gold, is soft enough to wear away rubbing against paper year after year. For this reason a "tipping material" is used on the part of the nib that touches paper. The tipping material could be stainless steel or some alloy of platinum group metals. Note that a stainless steel nib would not require tipping material.
As with all things, the reputation of the manufacturer and the price of the pen tells you an awful lot.
This outfit offers flex nibs as well as flex nib pens, and lots of other stuff. They are in Texas.
Tom's Pen Info / tom@mmto.org