Many years ago, I stopped at the Williams Gun Sight Company in Davison, Michigan and inquired as to the cost of having their irons installed on a couple of Ruger Model 77 rifles I had. I was quoted a price of over $100.00 each. I decided that modern made quality scopes probably negate any need for backup sights.
Penny-foolish and short-sighted.
Even crappy Chi-Com optics are running $400-$500. A good quality scope should cost as much or more than the rifle. *Most* rifles will shoot decently if the barrel is decent and the stock fit is correct.
The irons are supposed to be there, at least in modern times, as an emergency back-up for lens or reticle failure (fogged-up), etc.
Back in the day, of course, growing up on .22s and such, nobody gave this two-step procedure a second thought (i.e., zero irons first, then the optic). Young aspiring marksmen were schooled on how to actually hit a target with an iron-sighted rifle, calculate distance, use hold-overs, etc. Pretty much what the Johnny Appleseed movement offers today.
That's why, when fall rolls around and there's that early whiff of venison in the air, the thinking Fuddley hits the range and starts with the irons first - learning where his deer rifle will hit with them at a given distance. Then he properly zeros the irons with his load of choice
before mounting the scope.
Some modern rifle with a solid set of irons, like Ruger's GSR, make this such a simple task even the dumbest barnwood-buildin' hillbilly can do it.