I've been tinkering with an excel spreadsheet gear list for some time. One of the things that it does is calculate the cost of what I still need to buy and the estimated weight. In many cases, I'm using actual reported and published weights, but in other cases, I'm just doing a best s.w.a.g. that I can. In any case, I've been tinkering with the list a lot, mostly to reduce the number of items that I have to buy and substitute in items that I already own, as well as doing lots of research into alternatives to what I put down the first time, to save either money or weight or both.
There are a few reasons why I was reluctant to make some of these changes for some time, specifically on my existing tent and sleeping bags, which aren't necessarily backpack friendly or high quality. By this, what I mostly mean is that they weren't expensive--I actually find on further investigation that my tent is about as good a tent in terms of weight, at least, as I'm likely find anywhere. Most of the lightweight sleeping bag options are mummy bags, and frankly, I don't really like them much. So, I've gradually broken through a few of my preconcieved notions, which are all theoretical anyway. But the result is that as the cost to outfit myself has come down by about $1,000 from my first list, my gear weight has gone up a few pounds. And there's always the risk that I've been overly optimistic about the weight of some gear too, which means that I might be understating the weight of my chosen gear. I'll say that my total is probably give or take 5 lbs.--and almost certainly give rather than take, if it's going to swing from my estimate.
Definitions will vary from place to place on what lightweight means with regards to backpacking. Karen Berger's book on ultralight hiking considers anything over 25 pounds to be in "traditional" range. Wikipedia says anything over 30 lbs. (although light and ultralight is under 20--meaning that the entire 20-30 lbs. range is in a black hole or something.)
Without completely starting from scratch, spending a lot of money, and concentrating specifically on doing so, I can't seem to get my base back weight down below 25 lbs. Right now, my estimate for it is just over 25 lbs., actually--while my much more expensive "ultra" list is about 22 lbs.. Granted; I'm going with a fairly traditional internal frame pack, I decided not to replace my existing sleeping bags (which when we bought them, we had no concept of looking for lightweight options) and I'm unwilling to bail on the concept of a tradition (albeit small and fairly lightweight) tent. And that includes a bear cannister, which I won't always need to bring, depending on where I'm planning on hiking.
It doesn't seem to me to be worth it to do things like starting to cut off the handles of toothbrushes, drilling holes in my forks, or ordering expensive quilt and backpack kits that I have to make myself. It's clearly worth it to me to take on a few extra pounds of gear to avoid the hassle and expense. Despite the fact that my base pack weight seems kinda high, I look at my list and I don't think I'm willing to make much more in the way of sacrifices to it beyond what I've already got.
While ultralighters may balk, I estimate that my fully loaded, with food and water and everything, pack will weigh around 30-35 lbs; maybe nearer to 40 if I've been overly generous in my weight estimates for some gear. That's lighter than my pack weight as a teenager, and quite a bit lighter than anything my teenager compatriots carried, but it's obviously heavier than what someone like a Ray Jardine disciple would carry. Then again, my goal isn't to hike the PCT or the AT, my goal is to hike much shorter hikes where the longest I would do would be something like the JMT, or the Tahoe Rim Trail or the Wonderland Trail--and realistically most of my trips would be even shorter than that (the average of all my listed desired hikes, minus the JMT which is an outlier because it's more than twice as long as the next longest, is about 35 miles.) Other than spending big money to replace perfectly good stuff with other stuff that's a little bit lighter, or dramatically altering my strategy (i.e., going tentless or something) or getting rid of stuff, there's not much I can do to make the weight much better. And there's not much I can get rid of--I guess I could not bring extra clothes, and I could bring no-cook food and forego a camp stove, but even so I'm only saving a couple of pounds that way--and the sacrifice almost certainly isn't worth it.
Here's a picture of me, my daugher, and my folks at Glacier. This was just a short day hike off the Going to the Sun Road... which we couldn't complete because the highest portions of it were still snow-bound when we were there. Needless to say, we did this without gear...