What I notice on my bike is that when riding around without any gear, I use the top two rings, and when riding around loaded I use the bottom two rings. So the cost of my load is one ring, which is pretty significant if the standard is in the 44, 34, 24 range. or 67% extra energy. Some of that is pretty much indispensable, one might say the bike, water, racks, and bags. So if one is working with the 50% number, then that presupposes some degree of bike, rack, bag etc... One can decide on not doing the 50%, but once one is in, one needs some degree of gear to carry that stuff.

The relevance to the OP's question is one of whether one is calculating marginal pounds at all. In many cases the issue is how do you get the summit oxygen to the top camp on everest. All the effort, all the expenditure is there to get you your summit attempt. So in hot weather you need everything you need in order to carry the water that allows you to stay out there, or the food. The last pound you put in place costs all the other pounds to get there. Sure there are some rides where it is all about the misery index of carrying, or not carrying an espresso maker.

I come from a mountaineering and risk management background. So I am looking at stuff like will I be able to outrun a dog or bear with my load. Basically I can't outrun either with a load, but I can without a load. Just a fun example. A real example is heart conditions and blown knees and ankles, as I ride through my mid 50s. Doctor says I need a bypass, I am waiting for something better to come along for the moment. Every trip could theoretically kill me. Since the crash, every trip could cripple my knee. So there is no marginal pound or misery index that makes sense. But we are all in this situation, one way or another. ATMO. I have ended up on a few trips going down bad dead ends with difficult retreats, and had to shoulder the bike and cyclocross it. I have limits for that kind of thing. Can happen at a border or bridge where there is no accommodation for a bike. I have had vehicles that were two bikes wide come at me on bridges and I had to lift my bike over their heads to let them by.

The pros of carrying too much gear are not all that convincing to me. So think espresso maker. I don't drink that stuff anyway, but I do drink coffee. If I stop drinking coffee cold turkey, I get a headache. Has never happened to me on the first few days of a ride. I guess because I am oxygenating like an SOB. I would like to have a cup of coffee, but I am doing something different by going on a trip, I don't require all the stuff I do while at home because, frankly, I am not filling time in the same way.

Almost all ultralite gear is better in some way, other than just the weight, than heavier gear. For instance there are many ways in which tarps are better than tents. Just as tents are better than tarps in their own way. Overall, cars are far better than bikes, but we all accept that bikes are also better than cars. It should be the kind of trade-off that is pretty much in our biking DNA. So don't look at weight savings as a zero sum game. Look for gear that inspires and assists you in every way, and has no compromises, then you won't have to ask zero sum questions.