That's an extremely good point, and I think an oft-ignored concern about modern jets, which has made me ponder the economic viability and dominance of the air forces of the future. It might very well-be possible (and demonstrated in Ukraine) that these extremely sophisticated platforms have become unable to economically deliver payload to the enemy. This might be due to the sheer technological complexity needed for operating in a modern environment, or the wrong preconceptions of aircraft designers of what is required to actually win a war. Thus due to sheer economics, airpower might not be the dominant force on the battlefield it once was, for whatever reason I'm not interested in exploring in this post.
If we consider the cost of aircraft and their payloads, in todays dollars.
Aircraft | Payload(lbs) | Cost in 2025 $ | Cost/lbs |
B-29 | 20000 | 11m | $550 |
F-4 Phantom II | 18000 | 24m | $1300 |
F-15E | 23000 | 100m | $4300 |
F-22 | 8000 | 200m | $25000 |
While the comparison is not entirely fair, the raw physical reality cannot be ignored.
I think the case can be made that the 5th gen represents an extreme low point of combat effectiveness, in exchange for boutique capabilities, and the 6th gen's chief priority needs to be reducing Cost/lbs.