another way to look at it, maybe.

I notice (with my large hiking group) that there are those who go once or twice a year, backpacking. They don't use the bag a lot. They don't go more than a night, and they don't do high miles per day.

I on the other hand started to really hike a lot and started to volunteer for SAR - if that isn't motivation to get the pack skinny and light, I don't know what is - keeping up with that deputy means being light on your feet. I backpack every month, at least one night, often 2-7 nights. Depends on what's going on with training and how many searches, and what the hiking group is doing. I use my gear a lot, for different things.

Spending that initial $500 on two high fill power down quilts was the best thing I could have done - they have over and over proved to keep me comfy and warm in all the 3 season travels I've had, and each weighs 1 lb 6 oz. Each packs down to a small ball and they fit side by side in the bottom of my 40 liter pack. When hammocking I take both. When ground sleeping I take one and add in a NeoAir.

I can estimate that I will have years of ongoing use of them, and so they really were the cheapest option I could get. If I were going out a couple nights a year, picking up something heavier and cheaper (a synthetic would be cheapest) would have meant carrying more weight, probably a larger pack, but if I managed to find a cheap option that was actually also warm? It might last a good long time simply because I wasn't stuffing and restuffing it every other week. Keeping a cheap synthetic uncompressed can extend its lifespan if it's not used a lot.

Last year I borrowed a 0 degree North Face synthetic from someone for an anticipated winter trip. It had burn marks on the shell but the guy still used it because it still worked reliably for him as a winter bag. I literally could not get the thing in my pack! I couldn't get it in a compression sack! My 55 liter pack bag was full nearly to the top with this bag. Since I did not end up going on the trip I borrowed it for, that did not matter a whole lot. This year, with a bit of a gear scholarship from SAR, I was able to get a down 0 degree - a Marmot 650 fp bag. It fits in the same pack with room to spare for the other winter gear and clothes. A 800+ fp bag would have left me more room still, I'm sure, but it's a radical difference, and I don't mind the 4 lb weight of the bag at all, given that the synthetic was 2 lbs heavier... A 4 lb bag for winter for me is fine. I won't use it that much, and hopefully will get rides from the helicopter or the snow cat at least part of the time.... SAR being SAR. And if I do go recreational in winter, there's always a pulk!