I asked this question years ago. I think it helps as a buying strategy. Another analysis would be to identify all the small inexpensive items that can be replaced first. I found it more cost effective to tackle all the smaller items like cook kit, dropper bottles, stuff sacks, etc. Some items can cost less AND weigh less, like using a CCF sleeping pad vs heavier and more expensive self-inflating pad, or a simple tarp vs a tent.
You get into equipment weight "brackets," where you want to replace a moderately light item with a SUL or higher performance one. Insulated items are the perfect example--- you have a 20F synthetic bag that cost $150 and the next jump is a high end down bag that is double the price or more; likewise for high loft jackets. Hopefully, you can find that you can save x-ounces by buying a few $10 items vs saving the same weight by buying a $300 sleeping bag. Of course, once you get all the little things down to the minimum, you have painted yourself in a corner and have to spend a lot more to get any more reduction in weight. I think most come to a level that is comfortable in terms of weight and cost. Making reductions from an 8 pound base weight is my guesstimate for increasing costs per ounce.