"I have seen some estimates in the millions." What estimates? This sounds like you saw posts from random people on social media.
All that money would need to be spent updating guides and brochures anyway if only some bird names are changed, as you recommend in the petition. And a few million dollars for the federal government to spend over a period of several years is tiny, not "enormous," as you claim. It's a few pennies from each of us each year, which I, for one, am more than willing to spend to get better names for our birds. There's a reason that concern hasn't been discussed previously on COBirds.
For full disclosure, so you know where I'm coming from, I do not care about whether bird names are changed at all. I don't think any of it will matter either way within a few years. The time and energy you spend complaining and trying to fight a decision that's already been made could be better spent trying to come up with great new names for birds and influence those decisions.
Evan Carlson
Pueblo