Heather
A few tips from someone else who is pathelogically gone..
When I started out going light my rule of thumb was to buy a new item if it was about half as heavy as my old item, without regard to cost. I quickly halved my total base weight.
Then, reduced it by another 25%(about) and found that I had gone TOO light on some items, thus durability and comfort started to suffer. Examples are a very painful backpack, rainwear which tore up the first day I wore it, unstable stoves, etc.
Now that I am old and wise (uh, about 2 years later..)I realize I want to maximize (low Weight + Comfort + Durability) at the lowest possible cost.
For many items like a stove where Comfort is not applicable, it can be replaced with Convenience. The convenience of a Caldera Cone, or even a heavy Jetboil make them popular choices.
As for cost/ounce saved, the more you research, the less iterations you will go through and thus the less your total cost.
I iterated through 5 rain jackets to get from 2lbs to 10 ounces, paying a few hundred $ along the way. All I had to do was just 'buy a DIAD', but I did not know it existed!
About your upcoming possible purchase at REI; they have a lifetime money back warrantee. I consider anything bought there essentially free. When something I'm researching becomes available at REI that essentially removes the Cost term from the equation, and I buy. If I returned it they will turn around and sell it again at their 'yard sales' and someone else will make use of it.
Ask for specific recommendations for something you are considering, ask about it here on BPL; sometimes you will get suggestions you did not know about.