A lot of this is all about being on a continuum. The extra thickness should help charcoal last longer, but more so than that, having a kettle that doesn't leak will save even more fuel before and especially after the cook. Want real charcoal savings? There's a Summit Charcoal grill for that, right?
But let's not kid ourselves here. Nobody buys anything to "save" charcoal, you either can afford the gadget, and appreciate it, or not.
That's why this hobby is so great. We have choices, and most of them are fairly inexpensive compared to a lot of other things out there.