I can't see spacers adding weight, since low offset wheel simply have less metal removed. Some wheels will have deeper dishes if they are designed around that offset, but not usually.

I look at spacer cost the other way around. Spacers free me up to have five times as many wheels to choose from. The odds of finding a bargain that makes up for the $75 is pretty high. Also, with the 818 being new, it's safer to get too much offset and space to fit since you can buy the wheels, measure, then order the right spacers. If you have a no-spacer plan, the wheels better fit. The worst case scenario is that your low-offset wheels need to move in.