Jan brings up an excellent point and it sent me back to my "notes" to re-create what I was doing when I was taking those notes.
What I was doing was deciding, on the basis of weight which excellent crank set to use on a new build: a Rivendell Silver 3 or a Rene Herse. My notes, assigning an effective weight of 418g was a SWAG at trying to offset the extra weight penalty of using Rene Herse Chainrings. The Rene Herse drive side crank arm has almost no spider, and as a result is very light. Each Rene Herse chainring has most of a three arm spider, and that's a lot of material that weighs more. For comparison, I just now weighed a brand-new Rene Herse 46T ring and a generic cheap-o 110mm BCD 46T chainring. The Rene Herse weighs 106g and the cheap-o weighs 84g. Rene Herse rings are a lot nicer than cheap-ones rings, last a lot longer, shift better, are more beautiful, etc etc etc.
I was trying to do a light build, and I knew the lightest choice among cranks I love would be the Rene Herse. In the calculations, I figured I'd save about 50g with a Rene Herse 1x crank set in my setup. That 50g would cost me $500, or $10 per gram, because the Silver 3 was already on hand and therefore FREE. If I did not have the Silver 3 on hand, then it would have been about a $200 price difference, so around $4 per gram. It's hard to say what I would have chosen, if that had been the situation.
So, again, my 418g estimate was a guess at an apples to apples effective weight to account for Rene Herse rings being heavier than 110mm BCD rings. For the OP, I think that was a reasonably relevant number, but I did not make clear that it was my own guess.
Bill Lindsay
El Cerrito, CA