To be efficient with the Volcano, I recommend the dosing capsules and the easy valve dosing capsule adapter available on the Storz & Bickel website. With this you load about the same amount you would in a bong. I run 3 bags off one dose capsule and as another commenter said you can turn the vaped product into edibles. Easy one is putting it on some pb on a cracker. These capsules are also used in the crafty, mighty vaporizers and there is an adapter available for the plenty vaporizer as well.
I don’t know about the Volcano specifically, but I do know I have noticed a huge increase in effect and efficiency since I switched to a dry herb vape. When I make I smoke I use wayyyy more grind than I do for the vape. It’s also nice having the freedom to “adjust” my high and tailor it to what I want out of my strain for that day. And like other users have said you get the bonus if the ABV which does a really good job of getting you stoned.
When I switched from bongs and bubblers to the Volcano I probably saved about 25% right out of the gate. Then later on when I realized you need less in the chamber than it looks like I saved a bit more. I was at about 1.5oz/month back when I was combusting, now after 10 years of almost exclusively vaping I consume about 1oz/month.