That isn't objectively true, and it is even less true if a person is already doing something like long distance touring and still can't get their weight under control.

On the objective basis, reducing what one eats if it is already unhealthy food (as is generally the case with obesity, and even most "sensible" diets), leads to nutritional starvation, which just tweaks the desire to eat more. Healthy food generally is more expensive than unhealthy food, that is part of the reason that obesity is more of a problem in the underclass. McDonalds, which is getting slaughtered with competition from perceived healthy brands, like Sweetgreens, has just implemented the nuclear option of further lowering it's prices. Since the corn economy was implemented during the Nixon admin, the amount of time americans work to feed themselves has plummeted, while calories consumed have soared.

Of course healthy food can be extremely cheap if you juice your lawn, grow your own vegetables, or raise your own tofu. But the same is in the roots of ultralite gear, home sewn, and kits are still for sale today.

The majority of ways of saving gear weight are actually cheaper in several categories: 1) just not having some stuff, not buying it (or not bringing it); 2) Buying lighter stuff, so this may not actually be cheaper because of supply issues, but lighter materials or products are in most cases cheaper. Light nylon costs less than cordura, cordura costs less than ballistic, and waterproof heavy vinyls are often the most expensive. Bags made of silnylon are cheaper and lighter than waterproof bags used in boats and still airtight. Bag covers or liners are cheaper and lighter than Otliebs. Less pockets/dividers/zippers cost and weigh less than more pockets and dividers or zippers. Ponchos and leggings are cheaper (particularly when they were more popular) and lighter than technical jackets and pants.

One reason why we have Otliebs is because cordura packs don't seal from water well, particularly if they are penetrated with many zippers and pockets. But lighter pack cloths, are quite waterproof, and if delivered in roller type constructions would satisfy most wet uses. But fashion moved in the direction of very heavy panniers, and they ended up not being water proof, so we moved to even heavier fabrics that were able to sell the simpler designs. Designs that if we had just stuck with in lighter fabrics, none of this would have been necessary.

The only stupid expensive stuff is stuff like carbon frames, and the weight savings of maybe a pound or so, (touring or MTB weight carbon parts are not as light as racing parts) is not worth the expense and other limitations.

Of course one does have to eat anew every day, but one normally can go without buying new touring gear, so on that basis your point is well taken, but as far as necessary purchases are concerned cost of lightweight is not a major issue.